An Identification Manual to the Small Mammals of British Columbia

DAVID W. NAGORSEN
An IDENTIFICATION MANUAL
to the SMALL MAMMALS
OF BRITISH COLUMBIA
Ministry of Sustainable Resource Management
Ministry of Water, Land and Air Protection
Royal British Columbia Museum

An IDENTIFICATION MANUAL
to the SMALL MAMMALS
OF BRITISH COLUMBIA
DAVID W. NAGORSEN
Ministry of Sustainable Resource Management,
Ministry of Water, Land and Air Protection, Biodiversity Branch,
and Royal British Columbia Museum
March 2002

Abstract
This manual covers the 83 native and introduced marsupial, insectivore, bat,
lagomorph, and rodent species known to occur in British Columbia. It is
intended to serve as a standard reference for students and wildlife biologist
identifying voucher specimens or animals “in the hand” captured during field
studies. The manual has two independent sets of identification keys, one for
whole animals or museum study skins and the other for cleaned skulls. In
addition, a brief species account is provided for each of the 83 species. Each
account includes a description, body measurements and weight, information
on discriminating similar species, a range map, and illustrations of the species
and its skull. Technical terms are defined in a glossary; important references
and other useful identification manuals are listed in a bibliography.
NATIONAL LIBRARY OF CANADA CATALOGUING
IN PUBLICATION DATA
Nagorsen, David W.
An identification manual to the small mammals of British
Columbia
ISBN 0-7726-4745-3
1. Mammals – British Columbia – Identification.
2. Mammals – British Columbia – Classification. I. British
Columbia. Terrestrial Ecosystems Branch. II. British
Columbia. Biodiversity Branch. III. Royal British Columbia
Museum. IV. Title.
QL721.5.B7N33 2002 599'.09711 C2002-960071-5
© Province of British Columbia 2002

Table of Contents
Introduction ......................................................................................... 1
Acknowledgements ............................................................................. 3
How To Use This Manual ................................................................... 4
Checklist of Species ............................................................................. 5
Key to Mammalian Orders................................................................. 9
A. Key to Whole Animals ................................................................. 9
B. Key to Skulls ................................................................................. 10
Key to Whole Animals (Individual species) .................................. 11
Shrews and Moles (Insectivora) ...................................................... 11
Bats (Chiroptera) .............................................................................. 16
Hares, Rabbits, and Pikas (Lagomorpha) ....................................... 19
Rodents (Rodentia) .......................................................................... 20
Key to Skulls (Individual species).................................................... 29
Shrews and Moles (Insectivora) ...................................................... 29
Bats (Chiroptera) .............................................................................. 33
Hares, Rabbits, and Pikas (Lagomorpha) ....................................... 36
Rodents (Rodentia) .......................................................................... 38
Key to Chipmunk Genital Bones ...................................................... 53
A. Male Genital Bone (Baculum) .................................................... 53
B. Female Genital Bone (Baubellum) ............................................. 54

iv TABLE OF CONTENTS
Species Accounts ................................................................................. 55
Order Didelphimorphia: New World Opossums .......................... 57
Family Didelphidae: New World Opossums .............................. 57
Order Insectivora: Insectivores ....................................................... 58
Family Soricidae: Shrews.............................................................. 58
Family Talpidae: Moles ................................................................ 70
Order Chiroptera: Bats..................................................................... 73
Family Vespertilionidae: Vespertilionid Bats.............................. 73
Order Lagomorpha: Lagomorphs ................................................... 90
Family Ochotonidae: Pikas .......................................................... 90
Family Leporidae: Hares and Rabbits ......................................... 92
Order Rodentia: Rodents ................................................................. 98
Family Aplodontiidae: Mountain Beavers .................................. 98
Family Sciuridae: Squirrels .......................................................... 99
Family Geomyidae: Pocket Gophers .......................................... 117
Family Heteromyidae: Heteromyids .......................................... 118
Family Castoridae: Beavers ......................................................... 119
Family Muridae: Rats, Mice, Voles, and
Lemmings .................................................................................... 120
Subfamily Arvicolinae: Voles and Lemmings........................ 120
Subfamily Murinae: Old World Rats and Mice .................... 135
Subfamily Sigmodontinae: New World Rats and Mice ........ 138
Family Dipodidae: Jumping Mice and Jerboas .......................... 143
Family Erethizontidae: New World Porcupines ........................ 146
Glossary of Technical Terms ............................................................ 147
Bibliography ........................................................................................ 151
References Cited in Manual ............................................................ 151
Additional Useful References ......................................................... 153
List of Illustrations For Keys ........................................................... 9
Key To Mammalian Orders ............................................................ 9
Figure 1 Clawless opposable thumb on hind
foot of opossum ......................................................... 9
Figure 2 Mandible of opossum showing ramus
inflected inward ......................................................... 10

TABLE OF CONTENTS v
Figure 3 Mandible of placental mammal
showing ramus directed back ................................... 10
Figure 4 Side of rostrum of hare/rabbit
showing fenestration ................................................. 10
Figure5 Incomplete bony palate of bat .................................. 10
Figure 6 Complete bony palate of insectivore ........................ 10
Key To Whole Animals ................................................................... 11
Insectivores .................................................................................. 11
Figure 7 External body measurement ..................................... 12
Figure 8 Front foot (sole) of mole .......................................... 13
Figure 9 Front foot (sole) of shrew ......................................... 13
Figure 10 Fringe of hairs on hind foot ...................................... 13
Figure 11 No fringe of hairs on hind foot................................. 13
Figure 12 3 unicuspids readily visible in12 side view ............... 13
Figure 13 5 unicuspids readily visible in side view ................... 13
Figure 14 3rd unicuspid smaller than 4th................................. 14
Figure 15 1st upper incisor lacking a medial tine ..................... 14
Figure 16 1st upper incisor with a medial tine;
medial edge curved in front view ............................. 14
Figure 17 1st upper incisor with a medial tine;
medial edge incisor straight in front view ................ 14
Figure 18 More than 4 pairs of toe pads ................................... 15
Figure 19 Medial tine of 1st upper incisor
below pigmented area ............................................... 15
Figure 20 4 or fewer pairs of toe pads ....................................... 15
Figure 21 Medial tine on 1st upper incisor at or
above pigmented area ............................................... 15
Figure 22 Width of palm of forefoot less than its length ......... 15
Figure 23 Width of palm of forefoot equal or
greater than its length................................................ 15
Bats ............................................................................................... 16
Figure 24 Finger joints for ageing bats ...................................... 16
Figure 25 Visible fringe of hairs on edge
of tail membrane ....................................................... 17
Figure 26 No visible fringe of hairs on edge
of tail membrane ....................................................... 17
Figure 27 Calcar with a keel....................................................... 17
Figure 28 Calcar without a keel ................................................. 17

vi TABLE OF CONTENTS
Figure 29 Fur on underwing extends to a line
from knee to elbow.................................................... 18
Figure 30 Fur on underwing does not extend
to a line from knee to elbow ..................................... 18
Figure 31 Length of bare area on snout about
1.5 times the width across nostrils ........................... 18
Figure 32 Length of bare area on snout about
equal to width across nostrils ................................... 18
Lagomorphs ................................................................................. 19
Figure 33 Nape on back of head-cottontail rabbit ................... 19
Figure 34 No nape on back of head-snowshoe hare ................ 19
Rodents ........................................................................................ 20
Figure 35 Tail bushy with long hairs ......................................... 20
Figure 36 Tail not bushy without long hairs ............................ 20
Figure 37 Stripes and mantle on Golden-mantled
Ground Squirrel (Spermophilus lateralis) ................. 21
Figure 38 Stripes and mantle on Cascade Mantled
Ground Squirrel (Spermophilus saturatus) .............. 21
Figure 39 Oval pad on sole of marmot foot ............................. 22
Figure 40 Circular pad on sole of marmot foot........................ 22
Figure 41 External cheek pouches, long claws
on front foot .............................................................. 23
Figure 42 Body form of a typical “mouse-rat” rodent ............. 23
Figure 43 Body form of a “vole-lemming” rodent ................... 23
Figure 44 Naked tail with scaly annulations clearly visible...... 24
Figure 45 Tail haired with scaly annulations indistinct ........... 24
Figure 46 Elongated hind legs and feet of
Jumping Mouse (Zapus) ........................................... 24
Figure 47 Diagnostic external features
of Black Rat (Rattus rattus) ....................................... 25
Figure 48 Diagnostic external features of
Norway Rat (Rattus norvegicus) ................................ 25
Figure 49 Grooved upper incisors ............................................. 25
Figure 50 Upper incisors not grooved ...................................... 25
Key To Skulls ................................................................................... 29
Insectivores .................................................................................. 29
Figure 51 Lateral view of shrew skull showing
the different types of teeth . ..................................... 30
Figure 52 Dorsal and ventral view of shrew
skull showing measurements .................................... 30

TABLE OF CONTENTS vii
Figure 53 Dorsal view of mole skull showing
zygomatic arches. ...................................................... 30
Figure 54 Lateral view of 1st upper incisor of mole skull. ....... 30
Figure 55 Dorsal view of shrew skull showing
the absence of zygomatic arches. .............................. 30
Figure 56 Lateral view of 1st upper incisor
of shrew skull. ............................................................ 30
Figure 57 3 unicuspids readily visible in
side view ..................................................................... 31
Figure 58 5 unicuspids readily visible in side
view, 3rd unicuspid larger than 4th.......................... 31
Figure 59 5 unicuspids readily visible in side
view, 3rd unicuspid smaller than 4th ....................... 31
Figure 60 1st upper incisor lacking a medial tine ..................... 31
Figure 61 Mandibular measurements for
discriminating Sorex preblei
and Sorex cinereus. ..................................................... 31
Figure 62 Profile of rostrum of Pacific Water
Shrew (Sorex bendirii) ............................................... 32
Figure 63 Profile of rostrum of Water Shrew
(Sorex palustris) ......................................................... 32
Figure 64 1st upper incisor with a medial tine;
medial edge curved in front view ............................. 31
Figure 65 Pigmented ridge on upper incisors
separated by a groove ................................................ 32
Figure 66 1st upper incisor with a medial tine;
medial edge straight in front view ............................ 31
Figure 67 Pigmented ridge on upper unicuspids
not separated by a groove ......................................... 32
Figure 68 Medial tine of 1st upper incisor
above pigmented area ............................................... 32
Figure 69 Medial tine of 1st upper incisor
below pigmented area ............................................... 32
Bats ............................................................................................... 33
Figure 70 Teeth in a bat skull .................................................... 33
Figure 71 Measurements of a bat skull ..................................... 34
Figure 72 One upper incisor on each side
of skull ........................................................................ 34
Figure 73 More than one upper incisor on each
side of skull ................................................................ 34

viii TABLE OF CONTENTS
Figure 74 One upper premolar on each side of skull ............... 35
Figure 75 Two upper premolars on each side of skull ............. 35
Figure 76 Three upper premolars on each side of skull ........... 35
Figure 77 Braincase strongly elevated ....................................... 35
Figure 78 Braincase not strongly elevated ................................ 35
Figure 79 Forehead with a steep slope ...................................... 36
Figure 80 Forehead without a steep slope................................. 36
Lagomorphs ................................................................................. 36
Figure 81 Measurements on a lagomorph skull
(basilar length, maxillary toothrow length) ............. 37
Figure 82 No supraorbital process ............................................ 37
Figure 83 Single oval fenestration ............................................. 37
Figure 84 Skull with narrow supraorbital processes;
distinct interparietal bone ......................................... 37
Figure 85 Side of rostrum of hare/rabbit showing
fenestration ................................................................ 37
Figure 86 Skull with wide supraorbital processes;
fused interparietal bone ............................................ 37
Rodents ....................................................................................... 38
Figure 87 Morphology and measurements of rodent skull ..... 38
Figure 88 Nomenclature of prismatic molars of voles ............. 39
Figure 89 Large conspicuous infraorbital opening .................. 39
Figure 90 Small inconspicuous infraorbital opening ............... 39
Figure 91 Infraorbital opening on side of rostrum .................. 39
Figure 92 Infraorbital opening V-shaped in outline ................ 39
Figure 93 1st upper cheek tooth
with distinct crescent fold ......................................... 40
Figure 94 1st upper cheek tooth
without distinct crescent fold ................................... 40
Figure 95 Measurements on Jumping Mouse
(Zapus) skull ............................................................. 40
Figure 96 Lemming upper molars re-entrant
angles deeper on outer side ....................................... 40
Figure 97 Upper molars of Bushy-tailed
Woodrat (Neotoma cinerea) ...................................... 40
Figure 98 Upper molars with rows of cusps ............................. 41
Figure 99 Zygomatic plate of Bushy-tailed
Woodrat (Neotoma cinerea) ...................................... 41
Figure 100 Zygomatic plate of arvicoline rodent ...................... 41

TABLE OF CONTENTS ix
Figure 101 Re-entrant angles on upper molars
equal on outer and inner sides.................................. 41
Figure 102 Lower molars of Northern Bog
Lemming (Synaptomys borealis) ............................... 41
Figure 103 Lower molars of Brown Lemming
(Lemmus trimucronatus) ........................................... 42
Figure 104 Re-entrant angles deeper on inner
side of lower molars .................................................. 42
Figure 105 Re-entrant angles equal on outer
and inner side of lower molars ................................. 42
Figure 106 Posterior palate with a shelf ...................................... 42
Figure 107 Posterior palate with a median
spiny process .............................................................. 42
Figure 108 Post-palatal bridge of Southern Redbacked
Vole (Clethrionomys gapperi) ....................... 43
Figure 109 Post-palatal bridge of Northern Redbacked
Vole (Clethrionomys rutilus) ........................ 43
Figure 110 2nd upper molar with 3 triangles
and a posterior loop .................................................. 43
Figure 111 2nd upper molar without a posterior loop .............. 43
Figure 112 First mandibular molar with 4 closed triangles ....... 43
Figure 113 First mandibular molar with 5 or 6
closed triangles .......................................................... 43
Figure 114 3rd upper molar with 3 inner salient angles ............ 44
Figure 115 3rd upper molar with 4 inner salient angles ............ 44
Figure 116 Upper incisors protrude extensively
beyond nasals ............................................................. 44
Figure 117 Incisive foramina taper sharply in
posterior region to narrow slits ................................ 44
Figure 118 Upper incisors hidden by nasals ............................... 44
Figure 119 Upper incisors extend slightly beyond nasals .......... 44
Figure 120 Incisive foramina taper gradually in
posterior region ......................................................... 45
Figure 121 Incisive foramina taper abruptly in
posterior region but not to narrow slits ................... 45
Figure 122 Upper molars with 3 rows of cusps .......................... 45
Figure 123 Upper molars with 2 rows of cusps .......................... 45
Figure 124 Upper incisor notched in side view .......................... 45
Figure 125 Braincase rectangular with parallel
temporal ridges .......................................................... 46

x TABLE OF CONTENTS
Figure 126 Braincase rounded with temporal ridges curved ..... 46
Figure 127 Upper incisor with a groove on anterior face .......... 46
Figure 128 Upper incisor without a groove on anterior face .... 46
Figure 129 Flask shaped auditory bullae, upper
cheekteeth with outer projection .............................. 47
Figure 130 “8“ shaped premolar ................................................. 47
Figure 131 Prominent depression in basioccipital region ......... 48
Figure 132 Dorsal profile of skull straight .................................. 48
Figure 133 Postorbital processes at right angles
to main axis of skull .................................................. 48
Figure 134 Dorsal profile of skull convex ................................... 48
Figure 135 Postorbital processes directed backwards ................ 48
Figure 136 Posterior border of nasal bones V-shaped ............... 49
Figure 137 Posterior border of nasal bones
square or arched ........................................................ 49
Figure 138 Infraorbital opening simple and
rounded piercing the zygomatic plate ...................... 49
Figure 139 Infraorbital opening a canal that passes
between the rostrum and zygomatic plate ............... 49
Figure 140 Zygomatic arches converge anteriorly,
flattened horizontally ................................................ 50
Figure 141 Zygomatic arches parallel,
not flattened horizontally ......................................... 50
Figure 142 Interorbital region with a V-shaped notch .............. 51
Figure 143 Anterior ventral border of orbit
opposite the 1st upper molar .................................... 51
Figure 144 Anterior ventral border of orbit
opposite the 2nd upper premolar ............................. 51
Key To Chipmunk Genital Bones .................................................. 53
Figure 145 Measurements for male genital bone
(baculum) .................................................................. 53
Figure 146 Measurements for female genital bone
(baubellum) ............................................................... 54
Figure 147 Baubellum with a “U” shaped base
and tapered near the proximal end .......................... 54
Figure 148 Baubellum lacking a “U” shaped base and
not tapered near the proximal end ........................... 54

Introduction
As part of the province’s mandate to conserve biodiversity and endangered
species, inventory and field research on the small mammals of British Columbia
has increased substantially over the past few decades. Reliable identification
obviously is essential in these studies. Yet many small mammal species are
difficult to identify particularly in the field. Despite the importance of
accurate identification, at present no single publication exists that could serve
as a standard for identification. Identification keys developed specifically for
the province’s mammals are found in The Mammals of British Columbia
(Cowan and Guiguet 1965), but this handbook is now out-of-print and dated.
Four small mammals, Spotted Bat (Euderma maculatum), Merriam’s Shrew
(Sorex merriami), Preble’s Shrew (Sorex preblei), and the Tundra Shrew (Sorex
tundrensis) have been added to the provincial fauna since The Mammals of
British Columbia was last revised in 1965. Furthermore, the keys in Cowan
and Guiguet (1965) do not reflect recent taxonomic changes such as the
treatment of the Dusky Shrew (Sorex monticolus) and Vagrant Shrew (Sorex
vagrans), Keen’s Mouse (Peromyscus keeni) and Deer Mouse (Peromyscus
maniculatus), and Keen’s Long-eared Myotis (Myotis keenii) and the Northern
Long-eared Myotis (Myotis septentrionalis) as distinct species. New updated
identification keys are provided in the revised Royal British Columbia
Museum handbook series on the mammals of British Columbia (Nagorsen
and Brigham 1993, Nagorsen 1996) and a key to the rodent and lagomorph
species will be in included volume 4 (now in preparation). However, with the
discovery of Merriam’s Shrew and Preble’s Shrew in the Okanagan Valley in
1999 (Nagorsen et al. 2001) and unresolved identification problems associated
with the long-eared myotis bats, the keys in Nagorsen and Brigham (1993)
and Nagorsen (1996) require fine-tuning.
The objective of this publication is to provide an up-to-date identification
manual in the form of a single book that can be easily carried in the field by
wildlife biologists, foresters, conservation officers, naturalists, and students.
It will also be a useful reference for university or community college courses
that require identification of the province’s mammalian fauna. The manual
is restricted to the 83 native and introduced marsupial, insectivore, bat,
lagomorph, and rodent species known to occur in British Columbia (see the
Checklist for their common and scientific names). These orders include the
1

2 INTRODUCTION
small terrestrial mammals most often studied in provincial inventories and
the species with the most identification problems. Small carnivores such as
weasels, are excluded, although they could be considered “small mammals”
by some definitions. A Royal British Columbia Museum handbook on the
“Carnivores of British Columbia” is now in preparation and it will contain
detailed identification keys to the province’s carnivores.
This manual is designed to identify animals “in the hand” or voucher
specimens; it is not intended as a field guide for identifying sightings or
mammalian sign such as tracks. Two independent sets of identification keys
are provided, one for whole animals and the other for cleaned skulls. In
addition to the identification keys, there is a brief species account for each
species with a synoptic summary of the species’ description, identification
from similar species, and a provincial range map. The accounts are intended
to provide additional information that will assist with identification. A
glossary of technical terms used in the keys has been included; important
references on the mammalian fauna of British Columbia and other identification
manuals that may be useful to the reader are summarized in the
Bibliography.
Before you begin a study, prepare a list of potential species for your study
area. For distributional information, consult the species accounts in this
manual and the Royal British Columbia Handbooks (Cowan and Guiguet
1965; Nagorsen and Brigham 1993; Nagorsen 1996). Researchers are urged to
contact the Ministries of Sustainable Resource Management and Water, Land
and Air Protection, or the Royal British Columbia Museum. These organizations
can provide more specific information on the small mammals in your
study area, species of special interest, potential identification problems, and
guidelines for collecting voucher specimens. Careful consideration should be
given to voucher specimens and sampling techniques before you initiate a
study. Vouchers are essential to verify the identifications of some species.
Dead animals taken in kill traps or animals that die accidentally in live capture
studies should be kept for reference and future research. For species difficult
to identify, the researcher should consider taking a representative sample of
specimens as vouchers even in live capture studies. For details on vouchers
specimens see Voucher Specimen Collection, Preparation, Identification,
and Storage Protocol: Animals (Ministry of Environment, Lands and Parks,
Resources Inventory Branch 1999). Nonetheless, some small mammals
covered in this manual are considered potentially threatened or endangered;
sampling techniques that involve killing should be avoided for these species.
Users should be aware that the small mammals of British Columbia are
protected from direct harm under the provincial Wildlife Act, and taking
voucher specimens or even live capture of these animals require permits that
can be obtained from the regional offices of the Ministry of Water, Land and
Air Protection.

Acknowledgements
This publication was a co-operative project with the former Wildlife Branch,
British Columbia Ministry of Environment, Lands and Parks and the Royal
British Columbia Museum, initiated in 1992. I especially thank Laura Friis for
her continued support and encouragement. The many illustrations were
done by Bill Adams, Donald Gunn, and Michael Hames whose patience and
helpful suggestions were much appreciated. I am indebted to Arifin Graham
of Alaris Design for his production of the manuscript for desk-top publishing
and his unflagging support despite the many setbacks and delays associated
with the project. Nick Panter tested the keys and provided invaluable feedback;
Gail Harcombe coordinated final production of the manual. I thank
Dave Hatler for his unpublished weights and linear measurements of muskrats
and beaver and Tod Zimmerling for porcupine weights from his Ph.D.
dissertation.
The development of the identification keys, species descriptions, and
measurements were based largely on museum specimens. Most of my
research was based on the collections of the Royal British Columbia Museum
(Victoria) supplemented with the mammal collections of the American
Museum of Natural History (New York), Burke Museum (University of
Washington, Seattle), California Academy of Sciences (San Francisco), Cowan
Vertebrate Museum (University of British Columbia, Vancouver), Canadian
Museum of Nature (Ottawa), Museum of Vertebrate Zoology (University of
California, Berkeley), Royal Ontario Museum (Toronto), Slater Museum
(University of Puget Sound, Tacoma), and the United States National
Museum (Washington, DC). I thank those institutions for allowing me to
examine and measure British Columbian specimens in their collections.
Funding for production of this manual was provided by the BC Ministry
of Water, Land and Air Protection, the Royal British Columbia Museum, and
Forest Renewal BC.
3

4
How to use this manual
A key to mammalian orders is the first key in the manual. Once you have
determined the mammalian order, select the appropriate key for identifying
your animal. The key to whole animals is intended for use on restrained or
anaesthesized live animals, dead animals, or museum study skins. The key to
skulls is based on cranial or dental traits, and it is intended for use on voucher
specimens prepared as museum specimens, or skulls recovered in raptor
pellets. Unfortunately, the four chipmunk species found in the province
cannot be reliably identified from pelage or skull traits, and in some regions
they can only be discriminated from their genital bone morphology. Therefore,
a separate key to chipmunk genital bones in the manual is provided. This
key can only be applied to genital bone specimens that have been specially
prepared by clearing and staining.
All of the keys are dichotomous, with diagnostic characters arranged into
couplets; each couplet offers two mutually exclusive choices labelled a or b.
Begin with couplet number one and select either a or b. This will give you a
species name or direct you to another couplet in the key. By systematically
working through the various steps, the user will eventually arrive at an
identification. Consult the species account to verify that your identification is
consistent with the species’ description and range map.
An introductory section at the beginning of each key summarizes the
important diagnostic traits and pitfalls in identifying species of that group.
The author tried to avoid subjective characteristics (e.g., slightly smaller than
or slightly darker than) and instead emphasized presence or absence traits,
absolute size differences, and absolute colour or pelage pattern differences.
Although some of these mammals have restricted distributions in the province,
the author deliberately avoided geography in the keys (e.g., found only
in the Okanagan Valley). Accurate locality information may be lacking for
some individuals. Moreover, the precise range for many small mammals in
the province is unknown and excluding a species on the assumption that it is
absent from an area could be misleading. Similarly, designing separate keys
for different geographic regions of the province was not practical for a single
manual designed to cover the entire province.

Checklist of species
This is a list of the scientific and common names for the 83 mammalian species
(75 native and 8 introduced) covered in the manual. Common and scientific
names are based on The Vertebrates of British Columbia: Scientific and
English Names (Ministry of Environment, Lands and Parks, Resources
Inventory Branch 2000). Orders and families are arranged according to their
generally accepted phylogenetic sequence. The subfamilies of the rodent
family Muridae are ordered alphabetically. Genera within a family and species
within a genus are ordered alphabetically.
(I)= introduced species.
ORDER DIDELPHIMORPHIA: NEW WORLD OPOSSUMS
FAMILY DIDELPHIDAE: NEW WORLD OPOSSUMS
Didelphis virginiana Kerr North American Opossum (I)
ORDER INSECTIVORA: INSECTIVORES
FAMILY SORICIDAE: SHREWS
Sorex arcticus Kerr Black-backed Shrew
Sorex bendirii (Merriam) Pacific Water Shrew
Sorex cinereus Kerr Common Shrew
Sorex hoyi Baird Pygmy Shrew
Sorex merriami Dobson Merriam’s Shrew
Sorex monticolus Merriam Dusky Shrew
Sorex palustris Richardson Common Water Shrew
Sorex preblei Jackson Preble’s Shrew
Sorex trowbridgii Baird Trowbridge’s Shrew
Sorex tundrensis Merriam Tundra Shrew
Sorex vagrans Baird Vagrant Shrew
5

6 CHECKLIST OF SPECIES
FAMILY TALPIDAE: MOLES
Neurotrichus gibbsii (Baird) Shrew-mole
Scapanus orarius True Coast Mole
Scapanus townsendii (Bachman) Townsend’s Mole
ORDER CHIROPTERA: BATS
FAMILY VESPERTILIONIDAE: VESPERTILIONID BATS
Antrozous pallidus (Le Conte) Pallid Bat
Corynorhinus townsendii (Cooper) Townsend’s Big-eared Bat
Eptesicus fuscus (Beauvois) Big Brown Bat
Euderma maculatum (J. A. Allen) Spotted Bat
Lasionycteris noctivagans (Le Conte) Silver-haired Bat
Lasiurus blossevillii (Lesson and Garnot) Western Red Bat
Lasiurus cinereus (Palisot de Beauvois) Hoary Bat
Myotis californicus California Myotis
(Audubon and Bachman)
Myotis ciliolabrum (Merriam) Western Small-footed Myotis
Myotis evotis (H. Allen) Western Long-eared Myotis
Myotis keenii (Merriam) Keen’s Long-eared Myotis
Myotis lucifugus (Le Conte) Little Brown Myotis
Myotis septentrionalis (Trouessart) Northern Long-eared Myotis
Myotis thysanodes Miller Fringed Myotis
Myotis volans (H. Allen) Long-legged Myotis
Myotis yumanensis (H. Allen) Yuma Myotis
ORDER LAGOMORPHA: LAGOMORPHS
FAMILY OCHOTONIDAE: PIKAS
Ochotona collaris (Nelson) Collared Pika
Ochotona princeps (Richardson) Common Pika
FAMILY LEPORIDAE: HARES AND RABBITS
Lepus americanus Erxleben Snowshoe Hare
Lepus townsendii Bachman White-tailed Jackrabbit
Oryctolagus cuniculus (Linnaeus) European Rabbit (I)
Sylvilagus floridanus (J. A. Allen) Eastern Cottontail (I)
Sylvilagus nuttallii (Bachman) Nuttall’s Cottontail

CHECKLIST OF SPECIES 7
ORDER RODENTIA: RODENTS
FAMILY APLODONTIIDAE: MOUNTAIN BEAVERS
Aplodontia rufa (Rafinesque) Mountain Beaver
FAMILY SCIURIDAE: SQUIRRELS
Glaucomys sabrinus (Shaw) Northern Flying Squirrel
Marmota caligata (Eschscholtz) Hoary Marmot
Marmota flaviventris Yellow-bellied Marmot
(Audubon and Bachman)
Marmota monax (Linnaeus) Woodchuck
Marmota vancouverensis Swarth Vancouver Island Marmot
Sciurus carolinensis Gmelin Eastern Grey Squirrel (I)
Sciurus niger Linnaeus Eastern Fox Squirrel (I)
Spermophilus columbianus (Ord) Columbian Ground Squirrel
Spermophilus lateralis (Say) Golden-mantled Ground
Squirrel
Spermophilus parryii (Richardson) Arctic Ground Squirrel
Spermophilus saturatus (Rhoads) Cascade Mantled Ground
Squirrel
Tamias amoenus J. A. Allen Yellow-pine Chipmunk
Tamias minimus Bachman Least Chipmunk
Tamias ruficaudus (A. H. Howell) Red-tailed Chipmunk
Tamias townsendii Bachman Townsend’s Chipmunk
Tamiasciurus douglasii (Bachman) Douglas’ Squirrel
Tamiasciurus hudsonicus (Erxleben) Red Squirrel
FAMILY GEOMYIDAE: POCKET GOPHERS
Thomomys talpoides (Richardson) Northern Pocket Gopher
FAMILY HETEROMYIDAE: HETEROMYIDS
Perognathus parvus (Peale) Great Basin Pocket Mouse
FAMILY CASTORIDAE: BEAVERS
Castor canadensis Kuhl Beaver

8 CHECKLIST OF SPECIES
FAMILY MURIDAE: RATS, MICE, VOLES, AND LEMMINGS
Subfamily Arvicolinae: Voles And Lemmings
Clethrionomys gapperi (Vigors) Southern Red-backed Vole
Clethrionomys rutilus (Pallas) Northern red-backed Vole
Lemmus trimucronatus (Richardson) Brown Lemming
Microtus longicaudus (Merriam) Long-tailed vole
Microtus montanus (Peale) Montane Vole
Microtus oeconomus (Pallas) Tundra Vole
Microtus oregoni (Bachman) Creeping Vole
Microtus pennsylvanicus (Ord) Meadow Vole
Microtus richardsoni (DeKay) Water Vole
Microtus townsendii (Bachman) Townsend’s Vole
Ondatra zibethicus (Linnaeus) Muskrat
Phenacomys intermedius Merriam Heather Vole
Synaptomys borealis (Richardson) Northern Bog Lemming
Subfamily Murinae: Old World Rats and Mice
Mus musculus Linnaeus House Mouse (I)
Rattus norvegicus (Berkenhout) Norway Rat (I)
Rattus rattus (Linnaeus) Black Rat (I)
Subfamily Sigmodontinae: New World Rats and Mice
Neotoma cinerea (Ord) Bushy-tailed Woodrat
Peromyscus keeni (Rhoads) Keen’s Mouse
Peromyscus maniculatus (Wagner) Deer Mouse
Reithrodontomys megalotis (Baird) Western Harvest Mouse
FAMILY DIPODIDAE: JUMPING MICE AND JERBOAS
Zapus hudsonius (Zimmermann) Meadow Jumping Mouse
Zapus princeps J. A. Allen Western Jumping Mouse
Zapus trinotatus Rhoads Pacific Jumping Mouse
FAMILY ERETHIZONTIDAE: NEW WORLD PORCUPINES
Erethizon dorsatum (Linnaeus) Porcupine

Key To Mammalian Orders
A. KEY TO WHOLE ANIMALS
1a. Tail prehensile, clawless opposable thumb on hind foot (Fig. 1),
females with a marsupium ............................... Didelphimorphia–Opossums 1
1b. Tail not prehensile, no opposable thumb on hind foot,
females without a marsupium ............................................................................ 2
FIGURE 1
2a. Forelimb modified into a wing ..................................... Chiroptera–Bats (p. 16)
2b. Forelimb not modified into a wing ..................................................................... 3
3a. Pointed snout that extends well beyond the mouth,
eyes tiny .......................................................... Insectivora–Insectivores (p. 11)
3b. Snout not strongly pointed and not extending well beyond mouth,
eyes not tiny ......................................................................................................... 4
4a. Tail “powder-puff’ like, two pairs of upper incisors
.................................................................... Lagomorpha–Lagomorphs (p. 19)
4b. Tail not “powder-puff” like, one pair of upper incisors
.................................................................................. Rodentia–Rodents (p. 20)
1 Only one species occurs in the province, the North American Opossum (Didelphis virginiana)
9

10 KEY TO MAMMALIAN ORDERS
B. KEY TO SKULLS
1a. Five pairs of upper incisor teeth, angle of ramus of mandible directed
medially (Fig. 2) .......................................................... Marsupialia–Opossums
1b. Less than 5 pairs of upper incisors, angle of ramus of mandible directed
posteriorly (Fig. 3) ............................................................................................... 2
FIGURE 2 FIGURE 3
2a. No canine teeth, incisors separated from cheek teeth by a large gap ................. 3
2b. Canine teeth present, no gap separating incisors from cheek teeth ................... 4
3a. Two pairs of upper incisors, side of rostrum extensively fenestrate (Fig. 4)
.................................................................... Lagomorpha–Lagomorphs (p. 36)
3b. One pair of upper incisors, side of rostrum not extensively fenestrate
.................................................................................. Rodentia–Rodents (p. 38)
FIGURE 4
4a. Canine teeth large and conspicuous, differentiated from adjacent teeth,
anterior edge of bony palate strongly notched between incisors (Fig. 5)
....................................................................................... Chiroptera–Bats (p.33)
4b. Canine teeth inconspicuous, not differentiated from adjacent teeth, anterior
edge of bony palate not strongly notched between incisors (Fig. 6)
........................................................................ Insectivora–Insectivores (p. 29)
FIGURE 5 FIGURE 6

Key To Whole Animals
This key is intended for use on restrained or anaesthetized live animals,
dead animals, or museum study skins. You will require a millimetre rule
or metric callipers for body measurements (Fig. 7, p. 12) and a metric (grams)
weigh scale. A magnifying device is essential for examining dental traits such
as the relative size of the unicuspid teeth or medial tines of the upper incisors
of shrews, or the presence of grooves on the upper incisor teeth of rodents.
A dissecting microscope is ideal but, if you are working in difficult field
conditions, a portable hand lens with a battery-powered light source will
suffice. You can expose the teeth by pushing up the lips and gently opening
the mouth.
A. SHREWS AND MOLES (INSECTIVORA)
Some insectivore species can be identified from pelage colour, morphology of
the feet, or body size, but the identification of most shrews is based on dental
characters. Specimens that are badly decomposed or mutilated from insects,
slugs or other predators may be impossible to identify from external traits.
Old individuals with badly worn teeth are also problematic. For these individuals,
voucher specimens should be preserved for identification by an
expert. The user should be aware that several species of shrews that occur in
the province (e.g., Preble’s Shrew, Sorex preblei) are impossible to distinguish
from external traits and their identification can only be made by examination
of a cleaned skull.
1a. Front feet large with broad palms and long claws (Fig. 8) ................................ 11
(Talpidae–Moles)
1b. Front feet not enlarged, palms not broad, claws not long (Fig. 9) ...................... 2
(Soricidae–Shrews)
11

12 KEY TO WHOLE ANIMALS: SHREWS AND MOLES (INSECTIVORA)
d
b
FIGURE 7. SMALL MAMMAL BODY MEASUREMENTS. A: TOTAL LENGTH,
B: EAR LENGTH, C: TAIL VERTEBRAE LENGTH, D: FOREARM LENGTH,
E: HIND FOOT LENGTH
a
e
c

KEY TO WHOLE ANIMALS: SHREWS AND MOLES (INSECTIVORA) 13
FIGURE 8
FIGURE 9
2a. Total length greater than 130 mm, hind foot length greater than 18 mm,
hind foot with a fringe of stiff hairs (Fig. 10) ...................................................... 3
2b. Total length less than 130 mm, hind foot length less than 18 mm,
hind foot lacking a fringe of stiff hairs (Fig. 11) .................................................. 4
➤
FIGURE 10 FIGURE 11
3a. Dorsal fur black, feet and belly grey or silver-grey, tail distinctly bicoloured
with a paler underside ........................ Common Water Shrew (Sorex palustris)
3b. Dorsal fur dark brown, feet and belly dark brown, tail dark brown and not
bicoloured ................................................ Pacific Water Shrew (Sorex bendirii)
4a. When head is viewed laterally 3 unicuspid teeth are visible in the upper jaw
(Fig. 12), tail length usually less than 40% of the total length
.................................................................................... Pygmy Shrew(Sorex hoyi)
4b. When head is viewed laterally 5 unicuspid teeth are visible in the upper jaw
(Fig. 13), tail length usually greater than 40% of the total length ....................... 5
FIGURE 12 FIGURE 13

14 KEY TO WHOLE ANIMALS: SHREWS AND MOLES (INSECTIVORA)
5a. When head is viewed laterally, the 3rd unicuspid tooth larger than 4th
unicuspid (Fig. 13) .............................................................................................. 6
5b. When head is viewed laterally, the 3rd unicuspid tooth smaller than 4th
unicuspid (Fig. 14) .............................................................................................. 9
6a. First upper incisor lacks a medial tine (Fig. 15)
.................................................................... Merriam’s Shrew (Sorex merriami)
6b. First upper incisor with a medial tine (Figs. 16, 17) ........................................... 7
6A
➤
FIGURE 15
FIGURE 16
FIGURE 14
FIGURE 17
7a. Pelage appears tricoloured with the fur on the back contrasting sharply
from the paler sides and belly, body weight usually greater than 5.0 grams
............................................................................................................................. 8
7b. Pelage does not appeared tricoloured and the fur on the back does not contrast
sharply from the sides, body weight usually less than 5.0 grams
............. Common Shrew (Sorex cinereus) OR Preble’s Shrew (Sorex preblei) 2
8a. Fur on back blackish, fur on belly dark brown, tail length greater than 37 mm
................................................................. Black-backed Shrew (Sorex arcticus)
8b. Fur on back brown, fur on belly grey, tail length less than 37 mm
........................................................................ Tundra Shrew (Sorex tundrensis)
9a. Tail distinctly bicoloured, dark on dorsal surface and white underneath,
medial edge of 1st upper incisor curved in front view (Fig. 16)
............................................................ Trowbridge’s Shrew (Sorex trowbridgii)
9b. Tail not distinctly bicoloured, underside of tail pale brown or grey,
medial edge of 1st upper incisor straight in front view (Fig. 17) ...................... 10
2 Preble’s Shrew (Sorex preblei) and the Common Shrew (Sorex cinereus) can only be distinguished
by measurements taken from a cleaned skull.
➤
➤
9A
6B 6B
➤
➤
9B

KEY TO WHOLE ANIMALS: SHREWS AND MOLES (INSECTIVORA) 15
10a. Five or more toe pads on toes 2 to 5 (Fig. 18), medial tine on 1st upper incisor
positioned below the pigmented area (Fig. 19)
......................................................................... Dusky Shrew (Sorex monticolus)
➤
FIGURE 18 FIGURE 19
10b. Four or less toe pads on toes 2 to 5 (Fig. 20), medial tine on 1st upper incisor
positioned at or above the pigmented area (Fig. 21)
.......................................................................... Vagrant Shrew (Sorex vagrans)
➤
FIGURE 20 FIGURE 21
11a. Tail length about one half of the head and body length, width of forefoot
palm less than its length (Fig. 22) ................ Shrew-mole (Neurotrichus gibbsii)
11b. Tail length less than one half of the head and body length, width of forefoot
palm equal or greater than its length (Fig. 23) .................................................. 12
➤
➤
FIGURE 22 FIGURE 23

16 KEY TO WHOLE ANIMALS: SHREWS AND MOLES (INSECTIVORA)
12a. Total length greater than 175 mm, hind foot length greater than 24 mm
........................................................... Townsend’s Mole (Scapanus townsendii)
12b. Total length less than 175 mm, hind foot length less than 24 mm
............................................................................ Coast Mole (Scapanus orarius)
B. BATS (CHIROPTERA)
Fur colour, external measurements (Fig. 7, p.12) especially forearm length
and ear length, and the presence or absence of a keel on the calcar are the most
important traits for identifying live bats or museum study skins. The diagnostic
characteristics used in the keys are of adult bats. Nursing young cannot be
identified with this key and some of the size criteria cannot be applied to
immature bats that have not reached their full adult size. Immature bats can
be distinguished from adults by the swollen finger joints (Fig. 24) and dull
dark fur of the immatures. Note that although ear length is used in several
sections of the key to separate species, this trait has a high measuring error.
Keen’s Long-eared Myotis (Myotis keenii) and Western Long-eared Myotis
(Myotis evotis) cannot be reliably identified from external traits and their
identification requires a cleaned skull. There are several other species of bats
(e.g., Yuma Myotis, Myotis yumanensis vs. Little Brown Myotis, Myotis
lucifugus) where some individuals are impossible to identify with a 100
percent certainty from their external features alone and positive identification
may require a voucher specimen.
FIGURE 24
A. IMMATURE
B. ADULT
1a. Ear length greater than 28 mm ............................................................................ 2
1b. Ear length less than 28 mm ................................................................................. 4
2a. Dorsal fur jet black with three white spots on rump and shoulders
..................................................................... Spotted Bat (Euderma maculatum)
2b. Dorsal fur not jet black and lacking white spots ................................................. 3
3a. Nose with two prominent bumps, forearm length 40-45 mm
.................................... Townsend’s Big-eared Bat (Corynorhinus townsendii)
3b. Nose lacking two prominent bumps, forearm length 48-57 mm
............................................................................ Pallid Bat (Antrozous pallidus)

KEY TO WHOLE ANIMALS: BATS (CHIROPTERA) 17
4a. Fur orange or rusty red in colour
.............................................................. Western Red Bat (Lasiurus blossevillii)
4b. Fur not orange or rusty red ................................................................................. 5
5a. Fur on back with frosted or silver-tipped hairs .................................................. 6
5b. Fur on back without frosted or silver-tipped hairs ............................................. 7
6a. Upper surface of tail membrane covered with fur,
forearm length 50-57 mm ................................... Hoary Bat (Lasiurus cinereus)
6b. Upper surface of tail membrane furred only at the base,
forearm length 39-44 mm .......... Silver-haired Bat (Lasionycteris noctivagans)
7a. Obvious (visible with the naked eye) fringe of hairs on outer edge
of tail membrane (Fig. 25) ......................... Fringed Myotis (Myotis thysanodes)
7b. No obvious (visible with the naked eye) fringe of hairs on outer edge,
of tail membrane (Fig. 26) ................................................................................... 8
➤
➤
FIGURE 25 FIGURE 26
8a. Calcar with a prominent keel (Fig. 27) ................................................................ 9
8b. Calcar without a prominent keel (Fig. 28) ........................................................ 12
➤
FIGURE 27 FIGURE 28
9a. Forearm length greater than 35 mm, hind foot length greater than 9 mm ...... 10
9b. Forearm length less than 35 mm, hind foot length less than 9 mm ................. 11
10a. Underwing furred outward to a line extending from knee to elbow (Fig. 29),
forearm length 34-44 mm ......................... Long-legged Myotis (Myotis volans)
10b. Underwing not furred outward to a line extending from knee to elbow (Fig. 30),
forearm length 43-52 mm ............................... Big Brown Bat (Eptesicus fuscus)
➤

18 KEY TO WHOLE ANIMALS: BATS (CHIROPTERA)
➤
FIGURE 29 FIGURE 30
11a. Fur on back pale blonde to orange-yellow, contrasts sharply with blackish ears,
face, and wings; length of bare area on snout about 1.5 times width across
nostrils (Fig. 31) ............... Western Small-footed Myotis (Myotis ciliolabrum)
11b. Fur on back chestnut to brown, does not contrast sharply in colour with ears,
face, and wings; length of bare area on snout about equal to width across
nostrils (Fig. 32) ................................... California Myotis (Myotis californicus)
FIGURE 31 FIGURE 32
12a. Ears long (14-22 mm), usually extending far beyond
tip of nose when pushed forward ...................................................................... 13
12b. Ears short (10-16 mm), usually not extending far beyond
tip of nose when pushed forward ...................................................................... 14
13a. Ear length usually less than 18 mm, no distinct shoulder patches, tail membrane
lacking a fringe of tiny hairs (viewed with hand lens)
...................................... Northern Long-eared Myotis (Myotis septentrionalis)
13b. Ear length usually greater than 18 mm, usually distinct shoulder patches,
tail membrane with a fringe of tiny hairs (viewed with a hand lens)
........................................................ Keen’s Long-eared Myotis (Myotis keenii)
OR Western Long-eared Myotis (Myotis evotis) 3
14a. Fur on back long, sleek, and glossy, forearm length usually greater than 36 mm
.............................................................. Little Brown Myotis (Myotis lucifugus)
14b. Fur on back short and dull, forearm length usually less than 36 mm
..................................................................... Yuma Myotis (Myotis yumanensis)
3 The Western Long-eared Myotis (Myotis evotis) generally has a longer forearm and ear than
Keen’s Long-eared Myotis (Myotis keenii) but because their forearm and ear length measurements
overlap extensively they can not be identified from external traits. Myotis keenii can only
be reliably discriminated from Myotis evotis with skull measurements.
➤

KEY TO WHOLE ANIMALS: HARES, RABBITS, AND PIKAS (LAGOMORPHA) 19
C. HARES, RABBITS, AND PIKAS (LAGOMORPHA)
The pikas are easily distinguished from hares and rabbits by their small size
and short ears (see Fig. 7 for body measurements). In most areas of the
province, the only species of hare or rabbit is the Snowshoe Hare (Lepus
americanus) and identification is straightforward. However, identification
can be problematic in areas where the Snowshoe Hare co-occurs with
cottontail species (e.g., lower Fraser Valley or Okanagan Valley) or regions
where the Eastern Cottontail coexists with feral populations of the European
rabbit (e.g., southern Vancouver Island). Although the Snowshoe Hare
generally turns white in winter, animals in summer pelage resemble the pelage
colour of cottontails. Positive identification of problematic or immature
animals may require voucher specimens.
1a. Ears short (ear length less than 40 mm) and rounded,
no visible external tail ......................................................................................... 2
1b. Ears long (ear length greater than 40 mm) and elongated,
visible external tail ............................................................................................... 3
2a. Dorsal pelage grey with an indistinct pale grey collar on neck and shoulders,
ventral pelage whitish ..................................... Collared Pika (Ochotona collaris)
2b. Dorsal pelage brown with no distinct grey collar on neck or shoulders,
ventral pelage grey ....................................... Common Pika (Ochotona princeps)
3a. Rufous or brown nape on back of head (Fig. 33) ................................................ 5
3b. No nape on the back of head (Fig. 34) ................................................................. 4
FIGURE 33 FIGURE 34
4a. Ear length greater than 100 mm
...................................................... White-tailed Jackrabbit (Lepus townsendii)
4b. Ear length less than 100 mm ..................... Snowshoe Hare (Lepus americanus)
5a. Ear length usually greater than 80 mm, total length greater than 490 mm
.......................................................... European Rabbit (Oryctolagus cuniculus)
5b. Ear length usually less than 80 mm, total length less than 490 mm ................... 6

20 KEY TO WHOLE ANIMALS: HARES, RABBITS, AND PIKAS (LAGOMORPHA)
6a. Pelage dull grey colour, weight less than 700 g, ear length less than 60 mm
............................................................ Nuttall’s Cottontail (Sylvilagus nuttallii)
6b. Pelage brownish, weight greater than 700 g, ear length greater than 60 mm
.......................................................... Eastern Cottontail (Sylvilagus floridanus)
D. RODENTS (RODENTIA)
Diagnostic external traits for identifying this diverse group include pelage
colour and markings, relative size of the tail, hind foot length, and head and
body length (see Fig. 7 for body measurements). Some species are exceedingly
difficult, if not impossible, to identify confidently from external characters.
Positive identification of many of the arvicoline rodents (voles, lemmings) for
example, may require an examination of skulls for various cranial or dental
characters. In some parts of the province, an examination of the male or
female genital bones is necessary to identify chipmunks (Tamias). Note that
immature animals can be problematic to identify from criteria based on
absolute size; some pelage traits (e.g., the median reddish stripe of red-backed
voles Clethrionomys) may be indistinct in immature individuals.
1a. Upper part of body covered with long stiff quills................................ Porcupine
(Erethizon dorsatum)
1b. Upper part of body not covered with long stiff quills ......................................... 2
2a. Hind foot webbed ................................................................................................ 3
2b. Hind foot not webbed .......................................................................................... 4
3a. Broad tail flattened dorsal-ventrally, head and body length
greater than 400 mm ................................................. Beaver (Castor canadensis)
3b. Tail flattened laterally, not broad, head and body length
less than 400 mm .................................................. Muskrat (Ondatra zibethicus)
4a. Tail with long hairs and bushy (Fig. 35) ............................................................. 5
4b. Tail without long hairs and not bushy (Fig. 36) ................................................ 22
FIGURE 35 FIGURE 36
5a. Vibrissae extending well beyond ears to shoulders, underside of tail white,
5 digits on front foot ........................ Bushy-tailed Woodrat (Neotoma cinerea)
5b. Vibrissae not extending well beyond ears, underside of tail not white,
4 digits on front foot ............................................................................................ 6

KEY TO WHOLE ANIMALS: RODENTS (RODENTIA) 21
6a. Tail flattened in appearance, skin on side of body extends between front
and hind legs to form a gliding membrane
............................................... Northern Flying Squirrel (Glaucomys sabrinus)
6b. Tail not flattened, no gliding membrane present on side of body ...................... 7
7a. Light and dark longitudinal stripes present on the back .................................... 8
7b. No stripes present on the back .......................................................................... 13
8a. Light and dark stripes present on side of head, stripes on body consist of
5 black and 4 light stripes .................................................................................... 9
8b. No stripes on the side of head, stripes on body consist of 4 black and
2 light stripes ..................................................................................................... 12
9a. The four pale body stripes indistinct, hairs on the dorsal surface of the tail
with white or grey tips ................ Townsend’s Chipmunk (Tamias townsendii)
9b. The four pale body stripes distinct, hairs on the dorsal surface of the tail
with pale yellow to rufous tips........................................................................... 10
10a. Total length usually less than 195 mm; belly fur whitish-grey .............................
................................................................. Least Chipmunk (Tamias minimus) 4
10b. Total length usually greater than 195 mm; belly fur buffy or whitish-grey ...... 11
11a. Belly fur usually buffy, underside of tail orange
...................................................... Yellow-pine Chipmunk (Tamias amoenus) 4
11b. Belly fur usually whitish, underside of tail rufous
...................................................... Red-tailed Chipmunk (Tamias ruficaudus) 4
12a. Prominent black stripes bordering the two light stripes on back,
a conspicuous mantle of brown or reddish hairs on neck and shoulders
(Fig. 37) ............... Golden-mantled Ground Squirrel (Spermophilus lateralis)
12b. Black stripes bordering the two light stripes on back are indistinct or absent,
mantle on neck and shoulders inconspicuous or absent
(Fig. 38) ............ Cascade Mantled Ground Squirrel (Spermophilus saturatus)
FIGURE 37 FIGURE 38
4 Because size and belly fur colour varies geographically among subspecies of these species, in
some areas of the province these 3 chipmunk species are impossible to distinguish from fur
colour or size. They can only be positively identified from skulls or genital bone morphology.

22 KEY TO WHOLE ANIMALS: RODENTS (RODENTIA)
13a. Dorsal pelage with spotted or mottled pattern ................................................. 14
13b. Dorsal pelage not spotted or mottled ................................................................ 15
14a. Side of neck tawny brown, ventral side of tail predominately reddish
with black tip, hind legs and dorsal surface of feet grey to yellowish-brown
................................................. Arctic Ground Squirrel (Spermophilus parryii)
14b. Side of neck greyish, ventral side of tail a mix of black and white,
hind legs and dorsal surface of hind feet reddish-brown
............................... Columbian Ground Squirrel (Spermophilus columbianus)
15a. Body heavy and stout, tail length less than 50% head and body length ........... 16
15b. Body not heavy and stout, tail length about equal to head and body length .... 19
16a. Posterior pad on sole of hind foot oval in shape (Fig. 39) ................................ 17
16b. Posterior pad on sole of hind foot circular in shape (Fig. 40) ........................... 18
FIGURE 39 FIGURE 40
17a. Dorsal surface of feet dark brown; side of neck grizzled brown,
neck not distinct from side or back ................... Woodchuck (Marmota monax)
17b. Dorsal surface of feet yellowish to buffy; side of neck uniform buffy
to yellow, neck paler than side or back
................................................. Yellow-bellied Marmot (Marmota flaviventris)
18a. Dorsal pelage grizzled with a mix of white and black; individual guard hairs
bicoloured or tricoloured .......................... Hoary Marmot (Marmota caligata)
18b. Dorsal pelage light to chocolate brown not grizzled; individual guard hairs
unicoloured ................ Vancouver Island Marmot (Marmota vancouverensis)
19a. Head and body length greater than 220 mm, tail vertebrae length
greater than 190 mm, hind foot length greater than 60 mm ............................ 20
19b. Head and body length less than 190 mm, tail vertebrae length
less than 190 mm, hind foot length less than 60 mm ....................................... 21
20a. Dorsal pelage rust grey, ventral pelage yellow or orange, tips of tail hairs and
tufts behind ears reddish-orange ............. Eastern Fox Squirrel (Sciurus niger)
20b. Dorsal pelage grey, ventral pelage whitish, tips of tail hairs and
tufts of hairs behind ears whitish OR melanic with pelage black
or dark brown ............................... Eastern Grey Squirrel (Sciurus carolinensis)

KEY TO WHOLE ANIMALS: RODENTS (RODENTIA) 23
21a. Ventral pelage predominately yellow or orange,
....................................................... Douglas’ Squirrel (Tamiasciurus douglasii)
21b. Ventral pelage predominately white or grey
............................................................ Red Squirrel (Tamiasciurus hudsonicus)
22a. External cheek pouches present on each side of the mouth (Fig. 41)............... 23
22b. No external cheek pouches present on side of mouth ...................................... 24
23a. Front feet with long claws (Fig. 41), tail no more than 50% of head and
body length ............................ Northern Pocket Gopher (Thomomys talpoides)
23b. Front feet without long claws, tail longer than head and
body length ........................... Great Basin Pocket Mouse (Perognathus parvus)
24a. Tail markedly shorter than hind foot length and not readily visible,
long claws on front feet (Fig. 41) ............... Mountain Beaver (Aplodontia rufa)
24b. Tail equal to or longer than hind foot length and readily visible,
front feet without long claws ............................................................................. 25
25a. Conspicuous eyes and ears, ears not concealed in fur, long tail, sleek body
(Fig. 42) ............................................................................. 26 (“mice and rats”)
25b. Inconspicuous eyes and ears, ears concealed in fur, tail short, body stocky
(Fig. 43) .................................................................. 34 (“voles and lemmings”)
FIGURE 42 FIGURE 43
26a. Tail nearly naked, scaly with annulations readily visible (Fig. 44) ................... 27
26b. Tail haired, scales and annulations not readily visible (Fig. 45) ...................... 32
➤ FIGURE 41
➤

24 KEY TO WHOLE ANIMALS: RODENTS (RODENTIA)
FIGURE 44
FIGURE 45
27a. Hind legs and hind feet greatly elongated (Fig. 46) .......................................... 28
27b. Hind legs and hind feet not elongated .............................................................. 30
FIGURE 46
28a. Ventral pelage typically pure white with no buffy wash, usually no buffy patches
on chest, throat, or belly ............... Western Jumping Mouse (Zapus princeps) 5
28b. Ventral pelage white typically with buffy wash, buffy patches often on chest,
throat, or belly ................................................................................................... 29
29a. Total length usually greater than 230 mm, tail vertebrae length usually
greater than 140 mm ..................... Pacific Jumping Mouse (Zapus trinotatus) 5
29b. Total length usually less than 230 mm, tail vertebrae length usually
less than 140 mm ........................ Meadow Jumping Mouse (Zapus hudsonius) 5
30a. Hind foot length less than 20 mm, weight less than 30 g
............................................................................. House Mouse (Mus musculus)
30b. Hind foot length greater than 20 mm, weight greater than 30 g ....................... 31
5 The jumping mice show considerable geographic variation in size and ventral fur colour. In
areas of the province where two species co-occur, positive identification requires a skull.

KEY TO WHOLE ANIMALS: RODENTS (RODENTIA) 25
31a. Tail longer than head and body length, snout pointed, rump light and slender
(Fig. 47) ........................................................................ Black Rat (Rattus rattus)
31b. Tail less than head and body length, snout blunt, rump thick and heavy
(Fig. 48) ............................................................ Norway Rat (Rattus norvegicus)
LONGER THAN
HEAD & BODY
FIGURE 47
TAIL BODY
SHORTER THAN
HEAD & BODY
LIGHT, SLENDER
HEAVY, THICK
FIGURE 48
EAR EYE NOSE
32a. Total length of adults less than 150 mm, adult weight less than 15 g, distinct
groove on anterior face of upper incisors (Fig. 49)
..................................... Western Harvest Mouse (Reithrodontomys megalotis)
32b. Total length of adults greater than 150 mm, adult weight greater than 15 g,
upper incisors without a groove (Fig. 50) ......................................................... 33
FIGURE 49 FIGURE 50
33a. Tail vertebrae length of adults less than 98 mm
............................................................. Deer Mouse (Peromyscus maniculatus) 6
33b. Tail vertebrae length of adults greater than 98 mm
...................................................................... Keen’s Mouse (Peromyscus keeni) 6
LARGE
SMALL
LARGE POINTED
SMALL BLUNT
6 Tail length will only discriminate adults. This trait is not completely reliable as there is some
overlap among the two species. Moreover, the diagnostic measurement of 98 mm is derived
from a few island and mainland samples of Peromyscus maniculatus and Peromyscus keeni from
southwestern British Columbia that were identified from genetic criteria. The reliability of this
diagnostic measurement for discriminating the two species of Peromyscus in other regions
needs to be assessed.

26 KEY TO WHOLE ANIMALS: RODENTS (RODENTIA)
34a. Dorsal pelage with broad chestnut or rufous-brown median stripe ................ 35
34b. Dorsal pelage lacking broad chestnut or rufous-brown median stripe ............ 36
35a. Tail densely furred, tail with yellow on the underside
.......................................... Northern Red-backed Vole (Clethrionomys rutilus)
35b. Tail sparsely furred, tail with white or grey on the underside
........................................ Southern Red-backed Vole (Clethrionomys gapperi)
36a. Tail vertebrae length less than 50 mm .............................................................. 37
36b. Tail vertebrae length greater than 50 mm ......................................................... 43
37a. Tail roughly the same length as the hind foot, tail vertebrae length
less than 20% of total length .............................................................................. 38
37b. Tail distinctly longer than hind foot, tail vertebrae length greater
than 20% of total length .................................................................................... 39
38a. Tail sparsely furred, dorsal pelage short and grey or dull brown,
upper incisor with a groove (Fig. 49)
................................................. Northern Bog Lemming (Synaptomys borealis)
38b. Tail densely furred, dorsal pelage long and orange to brown.
upper incisors not grooved (Fig. 50)
........................................................ Brown Lemming (Lemmus trimucronatus)
39a. Fur short and velvety, eye diameter less than 3 mm
....................................................................... Creeping Vole (Microtus oregoni)
39b. Fur not short and velvety, eye diameter greater than 3 mm ............................. 40
40a. Tail thin, not thickened at base, and sparsely furred, body fur soft and fine
............................................................ Heather Vole (Phenacomys intermedius)
40b. Tail not thin, thickened at base, and covered in hairs, body fur coarse ........... 41
41a. Pelage grizzled grey-brown or salt and pepper appearance,
tops of hind feet whitish to grey
................................................................... Montane Vole (Microtus montanus)
41b. Pelage brown, not a salt and pepper pattern, tops of hind feet dark brown to
nearly black ....................................................................................................... 42
42a. Dorsal pelage with tinges of yellow on flanks and rump,
underparts pale yellow, tail strongly bicoloured
.................................................................. Tundra Vole (Microtus oeconomus) 7
42b. Dorsal pelage lacking yellow tinge on flanks and rump, underparts grey,
tail not strongly bicoloured
........................................................... Meadow Vole (Microtus pennsylvanicus) 7
7 Positive identification of these two species may require an examination of the morphology of
the 2nd upper molar in the skull.

KEY TO WHOLE ANIMALS: RODENTS (RODENTIA) 27
43a. Hind foot usually greater than 26 mm, adult body weight usually
greater than 100 g ......................................... Water Vole (Microtus richardsoni)
43b. Hind foot length usually less than 26 mm, adult body weight
less than 100g .................................................................................................... 44
44a. Tail vertebrae length usually 33% or more of the total length
........................................................... Long-tailed Vole (Microtus longicaudus)
44b. Tail vertebrae length usually less than 33% of the total length
............................................................. Townsend’s Vole (Microtus townsendii)

Key to Skulls
This key is based on cranial and dental characters; therefore, it is designed to
be used on cleaned skulls prepared as museum specimens (see Ministry of
Environment Lands and Parks, Resources Inventory Branch 1999) or skulls
recovered from raptor pellets. You will require a dissecting microscope to
examine teeth. For insectivores and bats, you can measure skull length with
needle-nosed callipers but accurate measurement of palatal length, interorbital
width, and toothrow length requires an ocular micrometer in a dissecting
microscope. All cranial and dental measurements used in the keys for the
lagomorphs and rodents can be taken with needle-nosed callipers. For
problematic specimens, voucher specimens should be submitted to a natural
history museum for verification.
A. SHREWS AND MOLES (INSECTIVORA)
Important diagnostic criteria include skull size, relative size of the unicuspid
teeth (Fig. 51), and position of the medial tine on the first upper incisor. Skull
length and palatal length (Fig. 52) are used as two measures of skull size.
Although this key is more reliable than the key to whole animals, it has its
limitations. Because of their fragility, skulls of insectivores taken in kill traps
or recovered in raptor pellets often have broken crania and their skull length
cannot be measured. Therefore, palatal length, a measurement that
can usually be taken from partial skulls, can be used as an alternate measure
of skull size in the key. Skulls of old individuals with badly worn teeth can be
difficult to identify because the pigmentation patterns and relative size of their
teeth may be obscured. For example, an important trait to distinguish the
Dusky Shrew (Sorex monticolus) from the Vagrant Shrew (Sorex vagrans) is
the position of the medial tine on the first upper incisor relative to the
pigmented region on this tooth. In old individuals, this pigmented region may
be completely worn away.
29

i
30 KEY TO SKULLS: SHREWS AND MOLES (INSECTIVORA)
u
p
1a. Skull with thin zygomatic arches (Fig. 53), 1st upper incisor not enlarged and
lacking a prominent hook (Fig. 54) .................................... 12 (Talpidae-Moles)
1b. Skull lacking zygomatic arches (Fig. 55), 1st upper incisor enlarged and with a
prominent hook (Fig. 56) .................................................. 2 (Soricidae-Shrews)
➤
M
FIGURE 51. SHREW SKULL WITH DIFFERENT
TYPES OF TEETH: I: 1ST UPPER INCISOR, U:
UNICUSPIDS, P: PREMOLAR, M: MOLARS
➤
FIGURE 53 FIGURE 54
FIGURE 55
c
b
a
FIGURE 52. INSECTIVORE SKULL MEASURE-
MENTS: A- A 1 : SKULL LENGTH, B-B 1 : PALATIAL
LENGTH, C-C 1 : WIDTH ACROSS 2ND UPPER
MOLARS M 2 .
FIGURE 56
2a. When skull viewed laterally, 3 unicuspid teeth visible (Fig. 57)
................................................................................... Pygmy Shrew (Sorex hoyi)
2b. When skull viewed laterally, 5 unicuspid teeth visible (Fig. 58, 59) ................... 3
3a. 3rd unicuspid tooth larger than 4th unicuspid (Fig. 58) .................................... 4
3b. 3rd unicuspid tooth smaller than 4th unicuspid (Fig. 59) .................................. 8
➤
c 1
➤
b 1
m 2
a 1

KEY TO SKULLS: SHREWS AND MOLES (INSECTIVORA) 31
FIGURE 57 FIGURE 58 FIGURE 59
4a. First upper incisor lacks a medial tine (Fig. 60) ...... Merriam’s Shrew (Sorex merriami)
4b. First upper incisor with a medial tine (Fig. 64, 66) ............................................. 5
FIGURE 60 FIGURE 64 FIGURE 66
5a. Skull length greater than 17.0 mm, palatal length greater than 7.2 mm ............ 6
5b. Skull length less than 17.0 mm, palatal length less than 7.2 mm ....................... 7
6a. Skull length greater than 18.5 mm, palatal length greater than 7.7 mm
................................................................. Black-backed Shrew (Sorex arcticus)
6b. Skull length less than 18.5 mm, palatal length less than 7.7 mm
........................................................................ Tundra Shrew (Sorex tundrensis)
7a. Skull length greater than 14.6 mm, length of mandible greater than 6.5mm
(Fig. 61) length of mandibular toothrow greater than 4.3 mm.
........................................................................ Common Shrew (Sorex cinereus)
7b. Skull length less than 14.6 mm, length of mandible less than 6.5 mm (Fig. 61) length of
mandibular toothrow less than 4.3 mm ............... Preble’s Shrew (Sorex preblei) 8
FIGURE 61
LENGTH OF MANDIBULAR TOOTHROW
LENGTH OF MANDIBLE
8 Because only 4 skulls of Preble’s Shrew (Sorex preblei) are available for the British Columbian
population, the diagnostic measurements that separate this species from Common Shrews
(Sorex cinereus) inhabiting the southern interior of the province are based on inadequate
samples. Any shrew suspected to be Preble’s Shrew (Sorex preblei) should be kept as a voucher
specimen and submitted to a natural history museum for verification.

32 KEY TO SKULLS: SHREWS AND MOLES (INSECTIVORA)
8a. Skull length greater than 19 mm, palatal length greater than 8.2 mm ............... 9
8b. Skull length less than 19 mm, palatal length less than 8.2 mm ........................ 10
9a. Rostrum long and curved ventrally in side view (Fig. 62)
................................................................. Pacific Water Shrew (Sorex bendirii)
9b. Rostrum short and straight in side view (Fig. 63)
............................................................ Common Water Shrew (Sorex palustris)
FIGURE 62 FIGURE 63
10a. Medial edge of 1st upper incisor appears curved in front view (Fig. 64, p. 31),
pigmented ridge on upper unicuspids separated from cingulum
by a longitudinal groove (Fig. 65)
............................................................ Trowbridge’s Shrew (Sorex trowbridgii)
10b. Medial edge of 1st upper incisor appears straight in front view (Fig. 66, p. 31)
pigmented ridge on upper unicuspids not separated from cingulum
by a longitudinal ridge (Fig. 67) ........................................................................ 11
FIGURE 65 FIGURE 67
11a. Medial tine on 1st upper incisor positioned at or above pigmented region
(Fig. 68), width across 2nd upper molars (M 2 -M 2 , Fig. 52) less than 4.5 mm
........................................................... ................ Vagrant Shrew (Sorex vagrans)
11b. Medial tine on 1st upper incisor positioned below pigmented region (Fig. 69),
width across 2nd upper molars (M 2 -M 2 ) greater than 4.5 mm
......................................................................... Dusky Shrew (Sorex monticolus)
➤
➤
FIGURE 68 FIGURE 69

KEY TO SKULLS: BATS (CHIROPTERA) 33
12a. Skull length less than 25.0 mm, palatal length less than 13.0 mm,
total of 36 teeth in skull ................................ Shrew-mole (Neurotrichus gibbsii)
12b. Skull length more than 25.0 mm, palatal length greater than 13.0 mm,
total of 44 teeth in skull ..................................................................................... 13
13a. Skull length greater than 37.0 mm, palatal length greater than 16.0 mm
........................................................... Townsend’s Mole (Scapanus townsendii)
13b. Skull length less than 37.0 mm, palatal length less than 16.0 mm
............................................................................ Coast Mole (Scapanus orarius)
B. BATS (CHIROPTERA)
Diagnostic cranial traits include the number of upper incisor and premolar
teeth (Fig. 70), cranial measurements (Fig. 71), and the shape of the forehead
and braincase. For species separated by skull shape such as the elevation of the
braincase or slope of the forehead, comparative reference specimens should
be examined to observe the different the different character states used in the
key. Most bats can be reliably identified from their skulls. Exceptions are the
Little Brown Myotis (Myotis lucifugus) and Yuma Myotis (Myotis yumanensis),
and the three species of long-eared myotis (Myotis keenii, Myotis septentrionalis,
and Myotis evotis). Most Myotis lucifugus and Myotis yumanensis can be
discriminated from each other by skull length and the shape of the forehead.
However, in some regions, there may be a few individuals that appear
intermediate in their cranial morphology. Skulls of the Long-eared Myotis
species are difficult to discriminate in areas where they overlap in their
distribution.
FIGURE 70. TYPES OF TEETH IN BAT SKULLS: I: UPPER
INCISORS, i: LOWER INCISORS, C: UPPER CANINE,
c: LOWER CANINE, P: UPPER PREMOLARS, p: LOWER
PREMOLARS, M: UPPER MOLARS, m: LOWER MOLARS.

34 KEY TO SKULLS: BATS (CHIROPTERA)
FIGURE 71. BAT SKULL MEASUREMENTS:A-A 1 : SKULL LENGTH, B-B 1 :
POSTORBITAL WIDTH, C-C 1 : WIDTH ACROSS FROM LAST UPPER MOLARS (M 3 -
M 3 ), D-D 1: LENGTH FROM LAST UPPER PREMOLAR TO LAST UPPER MOLAR (P 4 -
M 3 ), E-E 1 : LENGTH OF MAXILLARY TOOTHROW.
1a. One upper incisor on each side of skull (Fig. 72) ................................................ 2
1b. More than one upper incisor on each side of skull (Fig. 73) ............................... 4
FIGURE 72 FIGURE 73
2a. One upper premolar on each side of skull (Fig. 74)
........................................................................... Pallid Bat (Antrozous pallidus)
2b. Two upper premolars on each side of skull (Fig. 75) .......................................... 3
3a. Skull length greater than 15.0 mm ...................... Hoary Bat (Lasiurus cinereus)
3b. Skull length less than 15.0 mm .............. Western Red Bat (Lasiurus blossevillii)
4a. One upper premolar on each side of skull (Fig. 74) ..............................................
........................................................................ Big Brown Bat (Eptesicus fuscus)
4b. More than one upper premolar on each side of skull...........................................5

KEY TO SKULLS: BATS (CHIROPTERA) 35
FIGURE 74 FIGURE 75
FIGURE 76
5a. Two upper premolars on each side of skull (Fig. 75) .......................................... 6
5b. Three upper premolars on each side of skull (Fig. 76) ....................................... 8
6a. Skull length greater than 18.0 mm .............. Spotted Bat (Euderma maculatum)
6b. Skull length less than 18.0 mm ............................................................................ 7
7a. Postorbital width greater than 4.0 mm
.................................................... Silver-haired Bat (Lasionycteris noctivagans)
7b. Postorbital width less than 4.0 mm
..................................... Townsend’s Big-eared Bat (Corynorhinus townsendii)
8a. Postorbital width greater than 3.4 mm ............................................................... 9
8b. Postorbital width less than 3.4 mm ................................................................... 15
9a. Ratio of postorbital width/upper toothrow
length greater than 0.7 mm ............................................................................... 10
9b. Ratio of postorbital width/upper toothrow
length less than 0.7 mm ..................................................................................... 12
10a. Braincase strongly elevated (Fig. 77) ........ Long-legged Myotis (Myotis volans)
10b. Braincase not strongly elevated (Fig. 78) .......................................................... 11
FIGURE 77 FIGURE 78

36 KEY TO SKULLS: BATS (CHIROPTERA)
11a. Forehead with a steep slope (Fig. 79); skull length usually
less than 14.0 mm ........................................ Yuma Myotis (Myotis yumanensis)
11b. Forehead with a gradual slope (Fig. 80); skull length usually
greater than 14.0 mm ........................... Little Brown Myotis (Myotis lucifugus)
FIGURE 79 FIGURE 80
12a. Width across last upper molars (M3-M3 ) greater than 6.2 mm
................................................................... Fringed Myotis (Myotis thysanodes)
12b. Width across last upper molars (M3-M3 ) less than 6.2 mm .............................. 13
13a. Length across upper molars and last premolar (P4-M3 )
greater than 4.2 mm, maxillary toothrow length greater than 5.8 mm
.................................................... Western Long-eared Myotis (Myotis evotis) 9
13b. Length across upper molars and last premolar (P4-M3 )
less than 4.2 mm, maxillary toothrow length less than 5.8 mm
........................................................................................................................... 14
14a. Forehead with steep slope (Fig. 79)
....................................................... Keen’s Long-eared Myotis (Myotis keenii) 9
14b. Forehead with a gradual slope (Fig. 80)
..................................... Northern Long-eared Myotis (Myotis septentrionalis) 9
15a. Forehead with steep slope (Fig. 79)
.............................................................. California Myotis (Myotis californicus)
15b. Forehead with a gradual slope (Fig. 80)
.......................................... Western Small-footed Myotis (Myotis ciliolabrum)
C. HARES, RABBITS, AND PIKAS (LAGOMORPHA)
Important cranial traits for identifying species in this order include the
fenestration of the rostrum, the supraorbital processes, distinctness of the
interparietal bone, and cranial size (Fig. 81). Basilar length and maxillary
toothrow length are used as measures for skull size. Although basilar length
is a good index of skull size, it cannot be taken on broken skulls and may be
influenced by age. Maxillary toothrow length can be usually taken from
broken skulls and it is less affected by age variation than basilar length.
9 Because their measurements overlap to some extent, distinguishing the long-eared myotis bat
species from single cranial measurements is difficult. Their skulls should be submitted to a
natural history museum for verification.

KEY TO SKULLS: HARES, RABBITS, AND PIKAS (LAGOMORPHA) 37
FIGURE 81. LAGOMORPH SKULL MEASUREMENTS.
A: MAXILLARY TOOTHROW LENGTH, B: BASILAR LENGTH
1a. Skull lacking supraorbital processes (Fig. 82),
rostrum with single oval fenestration (Fig.83)
.................................................................. Collared Pika (Ochotona collaris) 10
OR American Pika (Ochotona princeps)
1b. Skull with supraorbital processes (Fig. 84),
rostrum with lattice like fenestration (Fig. 85) ................................................... 2
FIGURE 82 FIGURE 83
FIGURE 84 FIGURE 85
2a. Interparietal bone indistinct, fused to parietal bones (Fig. 86)
supraorbital processes broad and wing-like ....................................................... 3
2b. Interparietal bone distinct, not fused to parietal bones (Fig. 84)
supraorbital bone narrow and strap-like ............................................................ 4
A
FIGURE 86
10 Although they differ in pelage colour, The Collared Pika (Ochotona collaris) and American Pika
(Ochotona princeps) can not be discriminated by any single skull measurement. Nevertheless,
the two species in British Columbia are separated in their ranges by a hiatus of some 800 km.
B

38 KEY TO SKULLS: HARES, RABBITS, AND PIKAS (LAGOMORPHA)
3a. Basilar length greater than 69.0 mm, maxillary toothrow greater than
16.0 mm ........................................ White-tailed Jackrabbit (Lepus townsendii)
3b. Basilar length less than 69.0 mm, maxillary toothrow length less
than16.0m ................................................... Snowshoe Hare (Lepus americanus
4a. Tip of posterior extension of supraorbital process free of the braincase
.......................................................... European Rabbit (Oryctolagus cuniculus)
4b. Tip of posterior extension of supraorbital process touching the braincase ...... 5
5a. Basilar length greater than 57.0 mm, maxillary toothrow length
greater than 14.0 mm ....................... Eastern Cottontail (Sylvilagus floridanus)
5b. Basilar length less than 57.0 mm, maxillary toothrow length
less than 14.0 mm ............................... Nuttall’s Cottontail (Sylvilagus nuttallii)
D. RODENTS (RODENTIA)
Important cranial traits for identifying rodents include: size (skull length,
maxillary toothrow length) (Fig. 87); the morphology of the crowns of the
molar teeth (Fig. 88); and the size, shape and position of the infraorbital
opening (Figs. 89, 90). It may not be possible to use size to identify immature
animals where the skull is not completely developed. The cusp patterns that
distinguish the Old World murine rodents (rats) and the New World
sigmodontine rodents (deer mice) are not discernible in old animals with
worn teeth. However, enamel patterns on the molar teeth of most arvicoline
rodents (voles, lemmings), are not affected by tooth wear.
NASAL
BONE
A
INCISORS
NASAL
BONE
MOLARS
INCISOR
PALATE
MOLAR
INCISIVE
FORAMEN
B
FIGURE 87. RODENT SKULL
AND MEASUREMENTS. A: SKULL
LENGTH, B: MAXILLARY
TOOTHROW LENGTH

KEY TO SKULLS: RODENTS (RODENTIA) 39
➤
➤
ANTERIOR LOOP POSTERIOR LOOP
ANTERIOR LOOP
INNER SIDE
➤
➤
FIGURE 88. NOMENCLATURE OF A MANDIBULAR MOLAR
OF AN ARVICOLINE RODENT.
1a. Skull with large and conspicuous infraorbital opening (Fig. 89) ....................... 2
1b. Skull with small and inconspicuous infraorbital opening (Fig. 90) ................. 25
FIGURE 89 FIGURE 90
2a. Infraorbital opening on the side of the rostrum (Fig. 91)
.............................................. Great Basin Pocket Mouse (Perognathus parvus)
2b. Infraorbital opening not on side of rostrum ....................................................... 3
3a. Infraorbital opening exceeding the foramen magnum in size,
round in outline ............................................... Porcupine (Erethizon dorsatum)
3b. Infraorbital opening not exceeding the foramen magnum in size,
oval or V-shaped in outline. ................................................................................ 4
4a. Infraorbital opening oval in outline (Fig. 89) ..................................................... 5
4b. Infraorbital opening V-shaped in outline (Fig. 92) ............................................ 7
FIGURE 91 FIGURE 92
➤
OUTER SIDE
TRIANGLE
➤
➤
SALIENT ANGLE

40 KEY TO SKULLS: RODENTS (RODENTIA)
5a. First upper cheektooth (i.e., premolar) with a distinct
crescent fold at the base of the main cusp (Fig. 93)
...................................................... Pacific Jumping Mouse (Zapus trinotatus) 11
5b. First upper cheektooth (i.e., premolar) without
a distinct crescent fold at the base of the main cusp (Fig. 94) ........................... 6
6a. Incisive foramen length (Fig. 95) less than 4.2 mm,
maxillary toothrow length less than 3.7 mm
..................................................... Meadow Jumping Mouse (Zapus hudsonius)
6b. Incisive foramen length (Fig. 95) greater than 4.2 mm,
maxillary toothrow length greater than 3.7 mm
........................................................ Western Jumping Mouse (Zapus princeps)
B
FIGURE 96
FIGURE 93 FIGURE 94
➤
➤
➤
➤
FIGURE 95 A. INCISIVE FORAMEN LENGTH
B. MAXILLARY TOOTHROW LENGTH
7a. Crowns of molars with triangles or prisms
of dentine surrounded by enamel (Figs. 96, 97) ................................................. 8
7b. Crowns of molars with cusps
and lacking triangles or prisms (Fig. 98) .......................................................... 21
ANT.
➤
➤
dentine enamel
➤
OUTER
INNER
POST.
ANT.
A
dentine enamel
FIGURE 97
OUTER
INNER
POST.
11 This trait tends to variable and it is not discernible in animals with worn teeth. For animals taken
from areas of the Cascade Mountains where this species overlaps with the range of the Western
Jumping Mouse (Zapus princeps) skulls should be submitted to a museum for verification.

KEY TO SKULLS: RODENTS (RODENTIA) 41
ANTERIOR
ROW 3
ROW 2
ROW 1
FIGURE 98
OUTER
INNER
POSTERIOR
8a. Zygomatic plate extending anteriorly from zygomatic process of maxilla
(Fig. 99), molars with prisms not arranged in alternating triangles (Fig. 97)
......................................................... Bushy-tailed Woodrat (Neotoma cinerea)
8b. Zygomatic plate not extending anteriorly from zygomatic process of maxilla
(Fig. 100), molars with prisms arranged in alternating triangles (Fig. 96) ........ 9
9a. Length of maxillary toothrow greater than 14.0 mm
.............................................................................. Muskrat (Ondatra zibethicus)
9b. Length of maxillary toothrow less than 14.0 mm ............................................. 10
FIGURE 99 FIGURE 100
10a. Re-entrant angles deeper on outer side of upper molars,
1st and 2nd molar re-entrant angles extend to inner border of tooth (Fig. 96)
....................................................................................................................................................11
10b. Re-entrant angles not deeper on outer side of upper molars,
1st and 2nd molar re-entrant angles do not extend to inner border of tooth
(Fig. 101) ........................................................................................................... 12
11a. Mandibular molars lacking closed triangles on the outer sides (Fig. 102)
................................................. Northern Bog Lemming (Synaptomys borealis)
11b. Mandibular molars with closed triangles on the outer sides (Fig. 103)
........................................................ Brown Lemming (Lemmus trimucronatus)
ANT.
➤➤
OUTER
INNER
POST.
ANT.
➤
➤
INNER
OUTER
FIGURE 101 FIGURE 102
POST.

42 KEY TO SKULLS: RODENTS (RODENTIA)
12a. On mandibular molars, inner re-entrant angles deeper than outer
re-entrant angles (Fig. 104) ................ Heather Vole (Phenacomys intermedius)
12b. On mandibular molars, inner and outer re-entrant angles about
equal in depth (Fig. 105) ................................................................................... 13
ANT.
ANTERIOR
➤
➤
INNER
OUTER
➤
INNER
OUTER
FIGURE 103
POST.
POSTERIOR
FIGURE 104 FIGURE 105
13a. Bony palate terminates as a thin transverse shelf
extending between the last molars (Fig. 106) ................................................... 14
13b. Bony palate terminates as a sloping median ridge
between the last molars bordered by lateral pits (Fig. 107) .............................. 15
➤
14a. Posterior edge of the palate usually completely fused (Fig. 108)
...................................... Southern Red-backed Vole (Clethrionomys gapperi) 12
14b. Posterior edge of the palate usually incompletely fused (Fig. 109)
....................................... Northern Red-backed Vole (Clethrionomys rutilus) 12
➤
ANT.
➤➤
INNER
OUTER
FIGURE 106 FIGURE 107
➤
POST.
12 Development of the palate is related to growth and age. Some old Northern Red-backed Voles
(Clethrionomys rutilus) may have palates with their posterior edge completely fused and a few
immature Southern Red-backed Voles (Clethrionomys gapperi) may have palates with their
posterior edge incompletely fused. Skulls taken from areas of overlap among the two species
should be examined by an expert at a natural history museum.

KEY TO SKULLS: RODENTS (RODENTIA) 43
FIGURE 108 FIGURE 109
15a. Second upper molar with 3 closed triangles
and a round posterior loop (Fig. 110)
............................................................ Meadow Vole (Microtus pennsylvanicus)
15b. Second upper molar with 3 closed triangles
but lacking a posterior loop (Fig. 111) .............................................................. 16
ANT.
OUTER
INNER
POST.
OUTER
FIGURE 110 FIGURE 111
INNER
POST.
16a. First mandibular molar usually with 4 closed triangles (Fig. 112)
.................................................................... Tundra Vole (Microtus oeconomus)
16b. First mandibular molar with 5 or 6 closed triangles (Fig. 113) ........................ 17
ANT.
INNER
OUTER
15A
POST.
ANT.
ANT.
INNER
FIGURE 112 FIGURE 113
POST.
OUTER
15B

44 KEY TO SKULLS: RODENTS (RODENTIA)
17a. Third upper molar with 3 inner salient angles (Fig. 114)
....................................................................... Creeping Vole (Microtus oregoni)
17b. Third upper molar with 4 inner salient angles (Fig. 115) ................................. 18
ANT.
OUTER
INNER
POST.
INNER
OUTER
FIGURE 114 FIGURE 115
POST.
18a. When skull viewed dorsally, upper incisors protrude extensively
beyond the nasal bones (Fig. 116); incisive foramina
taper to narrow slits posteriorly (Fig. 117)
...................................................................... Water Vole (Microtus richardsoni)
18b. When skull viewed dorsally, upper incisors hidden
or protrude only slightly beyond the nasal bones (Fig. 118, 119);
incisive foramina not tapered to narrow slits posteriorly (Figs. 120, 121) ....... 19
➤
FIGURE 116
ANT.
FIGURE 117
FIGURE 118 FIGURE 119

KEY TO SKULLS: RODENTS (RODENTIA) 45
FIGURE 120 FIGURE 121
19a. When skull viewed dorsally, upper incisors hidden by the nasal bones (Fig. 118)
......................................................... Long-tailed Vole (Microtus longicaudus) 13
19b. When skull viewed dorsally, upper incisors extend slightly beyond
the nasal bones (Fig. 119) .................................................................................. 20
20 a.Incisive foramina taper gradually in the posterior region (Fig. 120)
.......................................................... Townsend’s Vole (Microtus townsendii) 13
20b. Incisive foramina taper sharply in the posterior region (fig. 121)
................................................................. Montane Vole (Microtus montanus) 13
21a. Cusps of first 2 upper molars arranged in 3 longitudinal rows (Fig. 122) ........ 22
21b. Cusps of first 2 upper molars arranged in 2 longitudinal rows (Fig. 123) ........ 24
ANT.
ROW 3
ROW 2
ROW 1
OUTER
INNER
POST.
ROW 2
ANT.
ROW 1
OUTER
INNER
FIGURE 122 FIGURE 123
22a. Upper incisor notched in side view (Fig. 124),
maxillary toothrow length less than 6.0 mm,
greatest length of skull less than 25 ..................... House Mouse (Mus musculus)
22b. Upper incisor not notched in side view,
maxillary toothrow length greater than 6.0 mm,
greatest length of skull greater than 25.0 mm ................................................... 23
FIGURE 124
13 Because the protrusion of the incisors and shape of the incisive foramina vary with age, these
traits are not completely reliable. Townsend’s Vole (Microtus townsendii) and the Montane
Vole (Microtus montanus) are widely separated in their ranges in British Columbia. However,
the Long-tailed Vole (Microtus longicaudus) co-occurs with M. townsendii in the lower Fraser
River valley and co-occurs with M. montanus in the interior grasslands. Discriminating the
skulls of these voles from these regions is difficult and identifications should be verified by an
expert at a natural history museum.
POST.

46 KEY TO SKULLS: RODENTS (RODENTIA)
23a. Braincase rectangular, temporal ridges straight
and nearly parallel (Fig. 125)
.......................................................................... Norway Rat (Rattus norvegicus)
23b. Braincase rounded, temporal ridges curved (Fig. 126)
...................................................................................... Black Rat (Rattus rattus)
FIGURE 125 FIGURE 126
24a. Upper incisor with a distinct groove on anterior face (Fig. 127),
maxillary toothrow length less than 3.8 mm,
skull length less than 23.0 mm
..................................... Western Harvest Mouse (Reithrodontomys megalotis)
24b. Upper incisors without a groove on anterior face (Fig. 128),
maxillary toothrow length greater than 3.8 mm,
skull length greater than 23.0 mm ................ Keen’s Mouse (Peromyscus keeni)
OR Deer Mouse (Peromyscus maniculatus) 14
FIGURE 127 FIGURE 128
14 Keens’ Mouse (Peromyscus keeni) and the Deer Mouse (Peromyscus maniculatus) can not be
discriminated by any single cranial measurement. For animals captured from coastal areas
where the two species co-occur voucher specimens should be submitted to a natural history
museum for verification.

KEY TO SKULLS: RODENTS (RODENTIA) 47
25a. Upper cheek-teeth with a distinct projection on outer side,
auditory bullae flask shaped (Fig. 129)
................................................................... Mountain Beaver (Aplodontia rufa)
25b. Upper cheekteeth lacking a distinct projection on outer side,
auditory bullae not flask shaped ....................................................................... 26
FIGURE 129
26a. Upper and lower premolars indented on the side forming an “8” shape
(Fig. 130) ............................... Northern Pocket Gopher (Thomomys talpoides)
26b. Upper and lower premolars not “8” shaped ..................................................... 27
➤
FIGURE 130
25B

48 KEY TO SKULLS: RODENTS (RODENTIA)
27a. Prominent depression in basiocciptal region (Fig. 131),
width of first upper cheek tooth greater than 9.5 mm
.................................................................................. Beaver (Castor canadensis)
27b. No prominent depression in basioccipital region,
width of first upper cheek tooth less than 9.5 mm ............................................ 28
FIGURE 131
28a. Dorsal profile of skull straight (Fig. 132),
interorbital region with a shallow depression,
postorbital processes at right angles to main axis of skull (Fig. 133) ............... 29
28b. Dorsal profile of skull convex (Fig. 134),
no shallow depression in interorbital region,
postorbital processes directed obliquely backwards (Fig. 135) ........................ 32
FIGURE 132
FIGURE 134
FIGURE 135
FIGURE 133

KEY TO SKULLS: RODENTS (RODENTIA) 49
29a. Length of maxillary toothrow greater than 21.2 mm ........................................ 30
29b. Length of maxillary toothrow less than 21.2 mm ............................................. 31
30a. Posterior border of nasal bones forms a V-shaped notch (Fig. 136)
.................................... Vancouver Island Marmot (Marmota vancouverensis)
30b. Posterior border of nasal bones square or arched (Fig. 137)
.................................................................... Hoary Marmot (Marmota caligata)
FIGURE 136 FIGURE 137
31a. Upper toothrows parallel, posterior border of nasal bones
forms a V-shaped notch (Fig. 136) ................... Woodchuck (Marmota monax)
31b. Upper toothrows diverge anteriorly, posterior border of nasal bones
forms an arch (Fig. 137) .......... Yellow-bellied Marmot (Marmota flaviventris)
32a. Infraorbital opening simple and rounded piercing the zygomatic plate
(Fig. 138), skull length less than 40.0 mm, maxillary toothrow length less than
7.0 mm ............................................................................................................... 33
32b. Infraorbital opening modified as a canal that passes between
the zygomatic plate and the side of rostrum (Fig. 139),
skull length greater than 40.0 mm, maxillary toothrow length greater than
7.0 mm ............................................................................................................... 35
FIGURE 138 FIGURE 139

50 KEY TO SKULLS: RODENTS (RODENTIA)
33a. Skull length greater than 37.0 mm,
maxillary toothrow length greater than 6.0 mm
.................................................... Townsend’s Chipmunk (Tamias townsendii)
33b. Skull length less than 37.0 mm,
maxillary toothrow length less than 6.0 mm .................................................... 34
34a. Skull length usually less than 32.5 mm,
mandibular length less than 17.5 mm ..... Least Chipmunk (Tamias minimus) 15
34b. Skull length usually greater than 32.5 mm,
mandibular length greater than 17.5 mm
..................................................... Red-tailed Chipmunk (Tamias ruficaudus) 16
OR Yellow-pine Chipmunk (Tamias amoenus) 16
35a. Zygomatic arches converge anteriorly and flattened in a horizontal plane
(Fig. 140) ........................................................................................................... 36
35b. Zygomatic arches parallel, not flattened in a horizontal plane (Fig. 141) ........ 37
FIGURE 140 FIGURE 141
36a. Skull length greater than 49.0 mm, maxillary toothrow greater than 10.0 mm
............................................... Arctic Ground Squirrel (Spermophilus parryii) 17
OR Columbian Ground Squirrel (Spermophilus columbianus) 17
36b. Skull length less than 49.0 mm, maxillary toothrow less than 10.0 mm
........................ Cascade Mantled Ground Squirrel (Spermophilus saturatus) 18
OR Golden-mantled Ground Squirrel (Spermophilus lateralis) 18
15 These diagnostic measurements will discriminate most Least Chipmunks (Tamias minimus)
from the Rocky Mountains and Columbia Mountains of southern British Columbia. However,
in northern areas of the province where this species is larger and co-occurs with the Yellowpine
Chipmunk (Tamias amoenus), the two species can only be positively identified from
genital bone morphology.
16 In southeastern British Columbia where the Red-tailed Chipmunk (Tamias ruficaudus) and
Yellow-pine Chipmunk (Tamias amoenus) co-occur, the two species overlap in size and they
can not be distinguished from any single skull measurement. Positive identification is based on
genital bone morphology or examination of skins and skulls by a natural history museum.
17 Although they show minor differences in their pelage, skulls of the Columbian Ground
Squirrel (Spermophilus columbianus) and Arctic ground Squirrel (Spermophilus parryii) can not
be discriminated by any single measurement. However, distributions of the two species in
British Columbia are widely separate.
18 Although they differ in their pelage colour and stripes, skulls of the Golden-mantled Ground
Squirrel (Spermophilus lateralis) and Cascade Mantled Ground Squirrel (Spermophilus
saturatus) can not be discriminated by any single measurement. However, distributions of the
two species in British Columbia are separate.

KEY TO SKULLS: RODENTS (RODENTIA) 51
37a. Interorbital region indented with a V-shaped notch (Fig. 142)
............................................... Northern Flying Squirrel (Glaucomys sabrinus)
37b. Interorbital region not indented with a V-shaped notch .................................. 38
FIGURE 142
38a. Skull length greater than 55.0 mm, maxillary toothrow greater than 10.0 mm,
anterior ventral border of orbit opposite the first upper molar (Fig. 143) ............ 39
38b. Skull length less than 55.0 mm, maxillary toothrow less than 10.0 mm,
anterior ventral border of orbit opposite the second upper premolar (Fig. 144)
.......................................................... Red Squirrel (Tamiasciurus hudsonicus) 19
OR Douglas Squirrel (Tamiasciurus douglasii) 19
FIGURE 143 FIGURE 144
39a. Two upper premolars
...................................................... Eastern Gray Squirrel (Sciurus carolinensis)
39b. One upper premolar
...................................................................... Fox Squirrel (Sciurus carolinensis)
19 Although these species generally differ in ventral pelage colour, their skulls can not be
discriminated from any single measurement. Specimens taken from areas on the eastern slopes
of the Cascade and Coast Mountains where the two species co-occur should be submitted to a
natural history museum for verification.

Key To Chipmunk Genital Bones
Because species convergence in pelage colour and size, chipmunks are difficult
or impossible to identify from pelage or even skull morphology in areas
of the province where two or more species co-occur. An important diagnostic
trait for discriminating chipmunk species is the morphology of the male and
female genital bones i.e., baculum and baubellum (White 1953; Sutton 1982).
Imbedded in the genitalia, these structures have to be specially prepared by
clearing the surrounding tissue with potassium hydroxide and staining with
Alazarin red, a stain that turns bone deep red. Preparation techniques are
given in White (1951) and Sutton (1982). Because they are minute, the genital
bones have to be viewed with a microscope and measured with an ocular
micrometer.
A. MALE GENITAL BONE (BACULUM)
1a. Shaft length (Fig. 145) greater than 3.20 mm,
keel height greater (Fig. 145) than 0.45 mm
....................................................... Red-tailed Chipmunk (Tamias ruficaudus)
1b. Shaft length less than 3.20 mm, keel height less than 0.45 mm .......................... 2
2a. Ratio of the tip length to shaft length (Fig. 145) greater than 30% ..................... 3
2b. Ratio of the tip length to shaft length less than 30%
................................................................. Least Chipmunk (Tamias minimus)
1 mm A. SHAFT LENGTH
B. TIP LENGTH
C. KEEL HEIGHT
A
FIGURE 145
C
B
53

54 KEY TO CHIPMUNK GENITAL BONES
3a. Tip length (Fig. 145) greater than 1.0 mm
.................................................... Townsend’s Chipmunk (Tamias townsendii)
3b. Tip length less than 1.0 mm
....................................................... Yellow-pine Chipmunk (Tamias amoenus)
B.FEMALE GENITAL BONE (BAUBELLUM)
1a. Greatest length (Fig. 146) greater than 2.0 mm, tip height (Fig. 146) greater
than 0.40 mm
....................................................... Red-tailed Chipmunk (Tamias ruficaudus)
1b. Greatest length less than 2.0 mm, tip height less than 0.40 mm ........................ 2
1 mm
B
A. GREATEST LENGTH
B. TIP HEIGHT
2a. Base “U” shaped base and usually tapered sharply near the proximal end
(Fig. 147) .................................... Townsend’s Chipmunk (Tamias townsendii)
OR Least Chipmunk (Tamias minimus) 20
2b. Base not “U” shaped and usually not tapered sharply near the proximal end
(Fig. 148) ....................................... Yellow-pine Chipmunk (Tamias amoenus)
➤
20 Baubella of Least Chipmunk (Tamias minimus) and Townsend’s Chipmunk (Tamias
townsendii) overlap in all measurements and are similar in general shape. However, the two
chipmunks are widely separated in their range in British Columbia and are easily discriminated
by skull size and pelage colour.
A
FIGURE 146
FIGURE 147 FIGURE 148
➤
➤

Species Accounts
A detailed species account is provided for each of the 83 species covered in the
identification keys. Species accounts follow the arrangement in the checklist.
Information in the species accounts is summarised under three headings:
Description, Similar Species, and Range.
Description is a concise description of the mammal including body measurements,
weight, and the dental formula. Descriptions of fur colour, body
measurements, and weights are based on adult museum specimens and live
animals from British Columbia. Exceptions were rare species known from
only a few specimens or captures from the province. For those species,
descriptions and measurements were based on museum specimens collected
from adjacent regions of western North America and the source of their
measurements and weights is noted in the account.
All linear body measurements (Fig. 7) are in millimetres. Weight (WT) is in
the nearest 0.1 grams (g) for animals weighing less than 1,000 grams and in
nearest 0.01 kilograms (kg) for animals weighing more than 1,000 grams.
Standard mammalian measurements given include total length (TL), tail
vertebrae length (TV), hind foot length (HF), and ear length (E). Body length
(total length minus tail vertebrae length) is given in some comparisons of
similar species. For bats, the forearm length (FA) and tragus length (TR) is
also included. The values given are the mean, range (in parentheses), and
sample size (number of individuals measured). For example, the mean total
length of the Snowshoe Hare is 443 mm, based on measurements obtained
from 139 animals with total lengths ranging from 388 to 530 mm—these
figures are written as “443 (388–530) n= 139”. Because weight varies with
season and reproductive condition, the reader should be aware that there
is considerable variation associated with the mean for each species. For
species with marked sexual dimorphism, separate weights are given for males
and females.
The dental formula describes the number of teeth in one side of the head (see
Figures 51, 70 and 87). The first number is the number in the upper jaw; the
second figure is the number in the lower jaw. For example, incisors 3/3,
canines 1/1, premolars 4/4, molars 3/3 for the Coast Mole (Scapanus orarius)
55

56 SPECIES ACCOUNTS
indicates three upper and lower incisors, one upper and lower canine, four
upper and lower premolars, and three upper and lower molars. The dental
formula for shrews includes the number of unicuspids. Which of the unicuspid
teeth are incisors, canines, and premolars is unknown.
Similar Species is a comparison with species that may be confused in identification.
Skull measurements used in comparisons are defined in Figures 52,
71, 81, and 87.
Range is a description of the provincial range. It includes a generalized range
map. The maps are not precise range maps and are only intended to assist the
reader with determining the species that may be present in a study area.
Provincial range maps showing dots for individual records are given in
Nagorsen and Brigham (1993) for bats and in Nagorsen (1996) for insectivores.

SPECIES ACCOUNTS 57
ORDER DIDELPHIMORPHIA: NEW WORLD OPOSSUMS
FAMILY DIDELPHIDAE: OPOSSUMS
Didelphis virginiana
(North American Opossum)
description: superficially appears
cat-like with a long pointed snout, naked
black ears with white or pink tips. The
prehensile scaly tail is furred at the base.
The fur is coarse with long guard hairs
and woolly underfur. Dorsal pelage
ranges from grey to white. A black colour
phase with black-tipped guard hairs
occurs in some populations. Females have
a pouch (i.e., marsupium); the hind foot
has an opposable thumb (Fig. 1). The
skull has 50 teeth including five pairs of
upper incisors.
External measurements: TL=753 (635–859) n=142,
TV= 286 (246–358) n=141, HF= 65 (57–78) n=142,
E= 55 (47–62) n=102, WT= 2.7 kg (1.5–4.1) n=54
males, 2.1 kg (1.5–2.9) n=80 females.
Dental Formula: incisors 5/4, canines 1/1, premolars
3/3, molars 4/4.
similar species: resembles no other British
Columbian mammal in external appearance. The
skull can be readily identified by 10 upper incisors
and a total of 50 teeth.
range: introduced into Oregon and Washington
and naturally spread into the lower
Fraser River valley where it occurs as far
east as Spuzzum. A population was recently
introduced to Hornby Island and
there are a few recent records from the
Victoria area on Vancouver Island.

58 SPECIES ACCOUNTS
ORDER INSECTIVORA: INSECTIVORES
Small mammals with long narrow snouts that extend well beyond the mouth,
short fur, small ears, minute eyes, and five digits on the front and hind feet.
The skull has a low braincase, long rostrum, teeth with numerous sharp cusps,
and canine teeth that are no larger than the incisors.
FAMILY SORICIDAE: SHREWS
Front feet are not enlarged; the external ears are small but visible. The skull
lacks zygomatic arches (Fig. 55), the first pair of upper incisors are enlarged
with a prominent hook (Fig. 56), and the teeth are pigmented with red.
Sorex arcticus
(Black-backed Shrew)
description: a medium-sized shrew with distinctive
tricoloured fur characterised by a blackish dorsal
band, brown sides, and greyish-brown belly. The
third unicuspid is greater or equal in size to
fourth (Fig. 13).
External measurements: TL= 116 (100–
125) n=30, TV= 41 (36–46) n=32,
HF= 14 (12–19) n=31, E= 7 (5–9)
n=8, WT= 9.4 g (6.0–13.0) n=10.
Dental Formula: incisors 1/1,
unicuspids 5/1, premolars 1/1,
molars 3/3.
similar species: although its range does not
overlap with S. arcticus, the Tundra Shrew (Sorex
tundrensis) is our only shrew of comparable size
that has similar markings and unicuspid teeth.
S. tundrensis has a brown dorsal stripe, shorter tail
(

SPECIES ACCOUNTS 59
Sorex bendirii
(Pacific Water Shrew)
description: the largest shrew in the
province, it has a dorsal pelage that
ranges from dark brown to black. The
undersides are dark brown. The tail
is unicoloured - dark brown. The
hind feet have a stiff fringe of hairs
(Fig. 10). The third unicuspid is smaller in size than the fourth (Fig. 14); the
rostrum of the skull is curved ventrally in side view (Fig. 62).
External measurements: TL= 154 (137–176) n=95, TV= 70 (61–81) n=94, HF= 19
(17–21) n=93, E= 8 (7–9) n=3, WT= 10.6 g (10.0–17.2) n=13.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: the large size (total
length >130 mm; hind foot >18 mm; skull
length >19.0 mm; palatal length >8.2 mm)
and stiff fringe of hairs on the hind feet
distinguish S. bendirii from all our other
shrew species except for the Water Shrew
(Sorex palustris). S. palustris can be identified
by: grey to black dorsal fur with a silvergrey
belly, a bicoloured tail that has a paler
underside, and a skull with the rostrum not
curved ventrally (Fig. 63).
range: restricted to the lower Fraser River
valley where it ranges east to Cultus Lake.
Northernmost records are from low elevations
on the north shore of Vancouver
(e.g., Mount Seymour Provincial Park).
There is an unconfirmed record from
Harrison Lake.

60 SPECIES ACCOUNTS
Sorex cinereus (Common Shrew)
description: a small shrew
with brown to dark brown dorsal
pelage that does not contrast
sharply with the fur on the sides.
The undersides are grey; the tail
is bicoloured. The skull is small
(skull length 18.5 mm,
palatal length >7.7 mm) and have a distinct
tricoloured pelage where the fur colour
on the back contrasts sharply from the
sides. S. merriami is easily identified by the
lack of a medial tine on the upper incisors. S. preblei can only be discriminated
by cranial and dental measurements (skull length

SPECIES ACCOUNTS 61
Sorex hoyi (Pygmy Shrew)
description: one of the smallest
shrews in British Columbia, it has dull
greyish-brown pelage and a relatively
short tail (

62 SPECIES ACCOUNTS
Sorex merriami
(Merriam’s Shrew)
description: a small shrew with
a dorsal pelage that varies from
grey to drab brown and pale nearly
white undersides 21 . The tail is distinctly
bicoloured. The teeth are
heavily pigmented with the third
unicuspid greater or equal to the
fourth (Fig. 13) and the upper incisors
lacking a medial tine (Fig. 15).
External measurements22 : TL= 82–94 n=12,
TV= 30–37 n=11, HF= 11–12 n=12, WT=
2.4–4.3 g n=11.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: the lack of medial tines
on the upper incisors is diagnostic and distinguishes
S. merriami from all other British
Columbian shrews.
range: known only from Kilpoola Lake in
the southern Okanagan Valley but may be
more widespread in
the intermontane
grasslands of the
province.
21 Because no skins are available from British Columbia, the pelage description is based on
descriptions of Merriam’s Shrew (Sorex merriami) from the western United Sates.
22 Only one decomposed specimen is available from British Columbia, measurements taken from
Verts and Carraway (1998).

SPECIES ACCOUNTS 63
Sorex monticolus
(Dusky Shrew)
description: a medium-sized
shrew with a dorsal pelage that
varies from greyish to dark brown
in interior populations to nearly
black in coastal populations.
The undersides are brown
to grey and the tail is not
distinctly bicoloured. The
toes (digits 2 to 5) have 5 or
more pairs of toe pads per toe (Fig. 18). The third unicuspid is smaller than
the fourth (Fig. 14), the medial edge of the first upper incisor appears straight
in front view (Fig. 66), and the pigmented ridge on upper unicuspids is not
separated from the cingulum by a longitudinal groove (Fig. 67).
External measurements: TL= 117 (93–140)
n=404, TV= 51 (35–68) n=436, HF= 14 (10–
18) n=436, E= 7 (4–9) n=198, WT= 6.6 g
(3.7–13.0) n=417.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: its range overlaps
with four other British Columbian shrews
that have the third unicuspid smaller than
the fourth: Pacific Water Shrew (S.
bendirii), Water Shrew (S. palustris),
Trowbridge’s Shrew (S. trowbridgii), and
Vagrant Shrew (S. vagrans).
S. bendirii and S. palustris are readily identified by their pelage colour, a fringe
of hairs on the hind feet, and large skulls (skull length >18.5 mm, palatal
length >7.7 mm). S. trowbridgii has a distinctly bicoloured tail, its first upper
incisors appear curved along the medial edge in front view (Fig. 66), and the
pigmented ridge on the upper unicuspids is separated from the cingulum by
a pronounced longitudinal groove (Fig. 65). These dental traits, however,
may not be discernible in old animals with badly worn teeth.
Discriminating S. monticolus from S. vagrans is difficult for old animals with
worn teeth and coastal populations where the pigmentation on the upper
incisors is weak. Preliminary studies (van Zyll de Jong 1982; van Zyll de Jong
1984) suggest that S. monticolus has more than four pairs of toe pads (Fig. 18)

64 SPECIES ACCOUNTS
on toes 2 to 5, but this has not been verified in a detailed study. S. monticolus
can also be distinguished by having the medial tine on the first upper incisor
positioned below the pigmented region (Fig. 19) and the width across the
second upper molars (M 2- M 2 ) >4.5 mm (Fig. 52).
range: the entire mainland and numerous coastal
islands including Vancouver Island and the Queen
Charlotte Islands.

SPECIES ACCOUNTS 65
Sorex palustris
(Common Water Shrew)
description: a large shrew
with an attractive dorsal pelage
that is usually dark grey or black
although some individuals
appear dull brown. The ventral
fur is silver-grey, sometimes
washed with brown. The tail is
distinctly bicoloured with dark
above and white or grey on the
undersides; the hind foot has a stiff fringe of hairs (Fig. 10). The third
unicuspid is smaller than the fourth (Fig. 14); the rostrum of the skull is not
curved ventrally (Fig. 63).
External measurements: TL= 152 (133–179)
n=179, TV= 75 (62–88) n=177, HF= 20 (16–
28) n=180, E= 7 (3–9) n=19, WT=10.6 g (7.5–
16.4) n=17.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: our only similar shrew
is the Pacific Water Shrew (S. bendirii);
distributions of the two species overlap in a
narrow zone in the north shore mountains
(Mount Seymour) and the lower Fraser
River valley (Cultus Lake). See the species
account for S. bendirii for diagnostic traits.
range: the entire mainland (except for the lower
Fraser River valley) and Vancouver Island.

66 SPECIES ACCOUNTS
Sorex preblei (Preble’s Shrew)
description: one of the smallest
shrews in British Columbia with a brown
dorsal pelage, silver-grey undersides, and
a distinctly bicoloured
tail. The third unicuspid
is greater or equal
to the fourth (Fig. 13).
External measurements23 : TL= 75 (71–77) n=3,
TV= 32 (32–33) n=3, HF= 10 (9–11) n=3, E=
9 n=1, WT= 1.9–2.8 n=10.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: the only species
S. preblei could be confused with are the
Common Shrew (S. cinereus) and Pygmy
Shrew (S. hoyi); see their accounts for diagnostic
traits.
range: known from the southern Okanagan Valley
and the Nicola Valley but may be more widespread in
the intermontane grasslands of the province.
23 Linear measurements from British Columbian specimens; weights taken from Verts and
Carraway (1998).

SPECIES ACCOUNTS 67
Sorex trowbridgii (Trowbridge’s Shrew)
description: a medium-sized
shrew with dark grey dorsal pelage,
and paler ventral fur. The tail is
distinctly bicoloured with
dark dorsal surface and white
underneath. The third unicuspid
is smaller than the
fourth (Fig. 14), the medial
edge of the first upper incisor
appears curved in front view (Fig. 16), the pigmented ridge on the upper
unicuspids is separated from the cingulum by a pronounced longitudinal
groove (Fig. 65).
External measurements: TL= 118 (101–128)
n=198, TV= 55 (41–62) n=198, HF= 13 (10–
15) n=193, E= 7 (5–8) n=5, WT= 5.6 g (3.8–
8.0) n=23.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: the grey pelage with
distinctly bicoloured tail with white on its
ventral surface is a diagnostic external trait.
The skull resembles the Dusky Shrew
(S. monticolus) and Vagrant Shrew
(S. vagrans); see those species accounts for
identification.
range: restricted to the lower Fraser Valley
where it ranges as far east as Chilliwack Lake
and Boston Bar. Northern records are
Vancouver and Harrison Lake.

68 SPECIES ACCOUNTS
Sorex tundrensis (Tundra Shrew)
description: a medium-sized
shrew with a striking tricoloured
pelage characterized by a brown
dorsal stripe, greyish-pale brown
sides, and a grey belly. The third
unicuspid is greater or equal in size
to the fourth (Fig. 13).
External measurements24 : TL= 97
(84–115) n=31, TV= 31 (25-37)
n=35, HF= 13 (10-15) n=34, E= 7
(4-7) n=12, WT=6.8 g (4.9-10.0)
n=29.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: although its range
does not overlap with S. tundrensis, the
Black-backed Shrew (S. arcticus) is our only
species with similar markings and skull
morphology. See its account for diagnostic
traits.
range: restricted to the Haines Triangle
of extreme north-western British Columbia
where it is known only from the Chilkat
Pass and Kelsall Lake along the Haines
Road.
24 Includes specimens from the Yukon Territory and western Northwest Territories.

SPECIES ACCOUNTS 69
Sorex vagrans (Vagrant Shrew)
description: a medium-sized shrew with a dorsal pelage that varies from
greyish in interior populations to dark brown or nearly black in coastal
populations. The undersides are brown
to grey; the tail is not distinctly
bicoloured. There are four
or less pairs of toe pads
on each toe [digits 2 to
5 (Fig. 20)]. The third
unicuspid is smaller than
fourth (Fig. 14), the medial
edge of the first upper incisor appears straight in front view (Fig. 17), and the
pigmented ridge on the upper unicuspids is not separated from the cingulum
by a longitudinal groove (Fig. 67).
External measurements: TL= 104 (85–126)
n=785, TV= 42 (32–58) n=793, HF= 12 (9–15)
n=803, E= 7 (5–9) n=530, WT=5.3 g (3.0–
10.0) n=801.
Dental Formula: incisors 1/1, unicuspids 5/1,
premolars 1/1, molars 3/3.
similar species: resembles S. trowbridgii
in cranial features and S. monticolus in external
and cranial traits. See those species
accounts for diagnostic traits.
range: Vancouver Island, the Gulf Islands,
the southern mainland as far north as Lac La
Hache and east to the Rocky Mountain
trench.

70 SPECIES ACCOUNTS
FAMILY TALPIDAE: MOLES
The limbs are short and close to the body; there are no external ears. The front
feet have broad palms and long claws (Fig. 8). The skull has thin zygomatic
arches (Fig. 53), the first pair of upper incisors are not enlarged with a hook,
and the teeth lack red pigment (Figs. 54).
Neurotrichus gibbsii
(Shrew-mole)
description: a small mole
that superficially appears
shrew-like. It has a long snout,
minute eyes hidden in the fur,
a long thick scaly tail that is
sparsely furred, and a forefoot with
the palm longer than wide (Fig. 22). The skull
has 36 teeth with only two pairs of upper and
lower premolars.
External measurements: TL= 102 (98–125) n=183,
TV= 37 (29–50) n=184, HF= 16 (14–19) n=184,
WT=11.1 g (8.0–14.5) n=33.
Dental Formula: incisors 3/3, canines 1/1,
premolars 2/2, molars 3/3
similar species: readily distinguished from
our other moles by: a long tail, front palms
longer than wide , small size (total length

SPECIES ACCOUNTS 71
Scapanus orarius (Coast Mole)
description: a stocky mole
with tiny eyes, short sparsely
furred tail, and front feet that
are enlarged with the palms
wider than long (Fig. 23). The
short velvety fur is greyishbrown
with a distinct sheen. The
skull has 44 teeth with four pairs
of upper and lower preomolars.
External measurements: TL= 162 (145–181)
n=129, TV= 33 (28–41) n=121, HF= 21
(18–24) n=128, WT= 69.1 g (46.0–78.1) n=
16 males; 56.6 g (45.6–66.9) n=15 females.
Dental Formula: incisors 3/3, canines 1/1,
premolars 4/4, molars 3/3
similar species: the only similar species
is Townsend’s Mole (S. townsendii).
The two species are similar in external
appearance and cranial traits and S.
townsendii can only be distinguished by
size: total length >175 mm, tail vertebrae
>24 mm, skull length >37.0 mm, palatal
length >16.0 mm.
range: the lower Fraser River valley east
to Hope.

72 SPECIES ACCOUNTS
Scapanus townsendii (Townsend’s Mole)
description: external
appearance and general
cranial traits identical to
S. orarius.
External measurements:
TL= 205 (179–237) n=30,
TL= 38 (31–45) n=30,
HF= 25 (23–29) n=31,
WT= 137.9 g (121.0–164.0)
n=7 males; 113.5 g (96.0–122.0)
n= 5 females.
Dental Formula: incisors 3/3, canines 1/1,
premolars 4/4, molars 3/3.
similar species: can only be confused
with the Coast Mole (Scapanus orarius);
see that account for diagnostic traits.
range: restricted to a localized area
around Huntingdon and Abbotsford in
extreme southwestern British Columbia.

SPECIES ACCOUNTS 73
ORDER CHIROPTERA: BATS
The forelimb is modified into a wing; the skull has a palatal emargination and
canine teeth that are larger than the incisors.
FAMILY VESPERTILIONIDAE: VESPERTILIONID BATS
Antrozous pallidus (Pallid Bat)
description: a large bat with short fine
fur that is light brown in colour. The ears are
long and broad; the tragus has a serrated
outer edge. The snout is square with a shallow
ridge. The calcar lacks a keel (Fig. 28).
The skull is large with robust teeth; it is the
only British Columbian bat with two pairs
of lower incisors.
External measurements: TL= 115 (110–121)
n=4, TV= 47 (44–51) n=4, HF= 13 (11–14)
n=4, E= 29 (28–30) n=3, TR= 15 n=1, FA=
54.4 (50.3–58.0) n=15, WT=20.1 g (17.1–24.3)
n=14.
Dental Formula: incisors 1/2, canines 1/1,
premolars 1/2, molars 3/3.
similar species: none.
range: known only from
the southern Okanagan
Valley from Okanagan
Falls to Osoyoos.

74 SPECIES ACCOUNTS
Corynorhinus townsendii (Townsend’s Big-eared Bat)
description: a medium-sized bat
with enormous ears and two prominent
glandular swellings or lumps on the nose.
The pelage varies from pale brown to
blackish-grey. The calcar lacks a keel
(Fig. 28).
External measurements: TL= 100 (83–113)
n=52, TV= 46 (38–57) n=44, HF= 11 (7–
10) n=51, E= 34 (27–40) n=26, TR= 13
(10–15) n=11, FA= 42.6 (39.0–45.2) n=55,
WT= 8.6 g (6.0–13.5) n=15.
Dental Formula: incisors 2/3, canines 1/1,
premolars 2/3, molars 3/3.
similar species: the Pallid Bat
(A. pallidus) and Spotted Bat (Euderma
maculatum) are the only other bats in
the province with such large ears. A. pallidus is
larger (forearm 50-58 mm) and E. maculatum
is readily identified by its distinctive jet black
fur and white markings.
The Silver-haired Bat (Lasionycteris noctivagans)
is the only other British Columbian bat
that shares the same dental formula. The skull
of L. noctivagans can be distinguished by its
flatter profile.
range: On the coast,
this species inhabits
Vancouver Island, the
Gulf Islands, and the lower mainland. In the interior,
C. townsendii ranges north to Williams Lake and
east to Cranbrook.

SPECIES ACCOUNTS 75
Eptesicus fuscus (Big Brown Bat)
description: a large bat with long lax
fur with an oily sheen. The pelage ranges
from pale brown in interior populations to
dark brown in coastal populations. The ears
just reach the nose when pushed forward.
The calcar has a prominent keel (Fig. 27).
The robust skull has a flattened braincase,
heavy jaw, and large teeth.
External measurements: TL= 116 (98–131)
n=126, TV= 46 (37–55) n=123, HF= 12 (8–15)
n=115, E= 15 (11–21)n=53, TR= 8 (5–11)
n=40, FA= 47.5 (43.0–52.0) n=109, WT=15.2 g
(8.8–21.9) n=36.
Dental Formula: incisors 2/3, canines 1/1,
premolars 1/2, molars 3/3.
similar species: its larger size (forearm
>42 mm), longer fur, and two pairs of lower
premolars are traits that distinguish E. fuscus
from any of our Myotis species.
range: Vancouver Island, the coastal mainland
north to Terrace, and north to the Peace
River region in the interior. There are unconfirmed
records based on
echolocation calls from
as far north as the Liard
River region.

76 SPECIES ACCOUNTS
Euderma maculatum (Spotted Bat)
description: the fur is black with
white spots on the rump and shoulders.
The ears are enormous (ear >30 mm,
tragus >12 mm). The skull has an elongated
braincase with a gradually sloping
forehead. The dental formula is unique
among British Columbian bats.
External measurements: TL= 125 n=1,
TV= 55 n=1 HF= 10 n=1 E= 39 n=1,
TR= 14 n=1, FA= 51.2 (47.9–53.1) n=6,
WT= 17.9 g (16.2–21.4) n=5.
Dental Formula: incisors 2/3, canines 1/1,
premolars 2/2, molars 3/3.
similar species: none.
range: Fraser, Okanagan, Similkameen, and
Thompson valleys of the dry interior north to
Williams Lake and the
Chilcotin River.

SPECIES ACCOUNTS 77
Lasionycteris noctivagans (Silver-haired Bat)
description: the fur is dark brown or
black with some white or silver-tipped hairs
that give it a frosted appearance. The dorsal
surface of the tail membrane is lightly furred.
The ears are short and round; the calcar lacks
a keel (Fig. 28). The skull is flat in profile with
a blunt rostrum.
External measurements: TL= 100 (90–117) n=68,
TV= 41 (31–50) n=70, HF= 9 (6–11) n=69, E=
12 (9–15) n=17, TR= 7 (4–8) n=22, FA= 41.4
(39.1–43.9) n=56, WT=9.0 g (5.8–12.4) n=14.
Dental Formula: incisors 2/3, canines 1/1,
premolars 2/3, molars 3/3.
similar species: only the Hoary Bat
(L. cinereus) is similar in colour. L. noctivagans
is smaller (forearm

78 SPECIES ACCOUNTS
Lasiurus blossevillii (Western Red Bat)
description: a large bat with striking
orange to rusty red fur. A faint frosting is
visible on the tips of some hairs; the dorsal
surface of the tail membrane is densely
furred. The calcar has a keel (Fig. 27). The
skull has a short broad rostrum and rounded
high braincase; there is only one pair of
upper incisors.
External measurements25 : TL= 107 (87-120)
n=98, TV= 50 (35-60) n=98, HF= 9 (6-13)
n=97, E= 12 (9-14) n=81, TR= 6 (5-7) n=26,
FA= 38.8 (34.0-42.0) n=19, WT= 10.8 g (7.2-
18.5) n=73.
Dental Formula: incisors 1/3, canines 1/1,
premolars 2/2, molars 2/3.
similar species: no species resembles
L. blossevillii in colour. L. cinereus shares
the same dental formula but has a larger
skull (skull length >15 mm).
range: known from only two localities:
the Skagit River and Okanagan Falls.
25 Based on a series of specimens from California.

SPECIES ACCOUNTS 79
Lasiurus cinereus (Hoary Bat)
description: our largest bat, it has a
beautiful frosted pelage. The hairs on the
back are a mix of dark brown and grey
tinged with white. Yellow fur is present
on the throat, ears, and undersides of the
wing membrane. The dorsal surface of
the tail membrane is heavily furred. The
ears are round and short; the calcar has a
keel (Fig. 27). The skull has a short broad
rostrum and rounded high braincase;
there is only one pair of upper incisors.
External measurements26 : TL= 137 (125-144)
n=11, TV= 60 (50-66) n=10, HF= 12 (10-15)
n=12, E= 14 (13-16) n=4, TR= 9 (9-10) n=4,
FA= 54.5 (50.3-57.4) n=24, WT= 28.4 g
(20.1-37.9) n=43.
Dental Formula: incisors 1/3, canines 1/1,
premolars 2/2, molars 3/3
similar species: the pelage vaguely
resembles the Silver-haired Bat (L. noctivagans);
see that species account for
diagnostic traits. The skull is similar to that
of the Western Red Bat (L. blossevillii) but
is larger in size (see previous account).
range: Vancouver Island, the southern mainland
north to Garibaldi Provincial Park, and the interior
north to Williams Lake. There are unconfirmed
records based on echolocation calls from as far
north as the Liard River region.
26 Forearm lengths and weights include a sample from Alberta.

80 SPECIES ACCOUNTS
Myotis californicus (California Myotis)
description: one of our smallest Myotis
species, its pelage ranges from rusty brown in
interior populations to blackish brown in coastal
populations. The calcar has a prominent keel
(Fig. 27). The skull is small with a steeply sloped
forehead (Fig. 79).
External measurements: TL= 80 (65–95) n=75,
TV= 36 (26–41) n=77, HF= 6 (5–9) n=80, E= 13
(8–15) n=40, TR= 4 (4–8) n=35, FA= 32.1 (29.4–
35.0) n=68, WT= 4.4 g (3.3–5.4) n=26.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: the small skull (postorbital
width

SPECIES ACCOUNTS 81
Myotis ciliolabrum
(Western Small-footed Myotis)
description: one of our smallest
Myotis species, the dorsal pelage is pale
tan to buff. Its black ears, snout, and wing
membranes contrast strongly with the
paler dorsal fur. The calcar has a keel (Fig.
27). The skull is small with a gradually
sloped forehead (Fig. 80).
External measurements: TL= 83 (72–90)
n=44, TV= 38 (32–45) n=44, HF= 7 (6–8)
n=44, E= 13 (8–15) n=25, TR= 7 (4–9)
n=24, FA= 31.8 (28.8–33.4) n=47, WT= 4.6
g (2.8–5.5) n=23.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: the California
Myotis (M. californicus) is the only bat
as small and with a keeled calcar. See
that account for diagnostic traits.
range: the Fraser, Okanagan,
Similkameen, and Thompson valleys of
the dry interior, north to Williams Lake.

82 SPECIES ACCOUNTS
Myotis evotis (Western Long-eared Myotis)
description: a large Myotis with long
ears (usually >18 mm). The fur colour is
extremely variable ranging from nearly black
on the coast to brown in the dry interior.
Distinct shoulder patches are evident on
paler individuals but they may be indistinct
in coastal populations. The calcar lacks a
distinct keel (Fig. 28). A fringe of tiny hairs
(visible with a hand lens) is present on the
outer edge of the tail membrane.
External measurements: TL= 92 (74–103)
n=54, TV= 42 (31–50) n=51, HF= 9 (7–11)
n=51, E= 20 (17–22) n=31, TR= 10 (8–12)
n=21, FA= 38.6 (36.0–42.0) n=47, WT= 5.5 g
(4.2–8.6) n=25.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: the distribution
overlaps with three other long-eared
Myotis species in British Columbia:
Keen’s Long-eared Myotis (M. keenii),
Northern Long-eared Myotis (M.
septentrionalis), and Fringed Myotis (M.
thysanodes). M. thysanodes) is larger
(forearm usually >42 mm), and has a
very prominent fringe of hairs on the
outer edge of the tail membrane that is
visible with the naked eye. The skull of
M. thysanodes has a broader palate
(width across upper molars, M2-M2 >6.2
mm). M. septentrionalis has smaller ears
(usually

SPECIES ACCOUNTS 83
these traits overlap with M. evotis. Positive identification can only be made
from a multivariate discriminant analysis using a number of skull and dental
measurements (see van Zyll de Jong and Nagorsen 1994).
range: Vancouver Island, coastal mainland north to
the Bella Coola Valley, interior north to the Liard River
region.

84 SPECIES ACCOUNTS
Myotis keenii (Keen’s Long-eared Myotis)
description: a medium-sized
Myotis with dark fur and indistinct
shoulder patches. A tiny fringe of hairs
is evident on the outer edge of the tail
membrane. The ears are long (usually
>16 mm); the calcar lacks a distinct
keel (Fig. 28).
External measurements: TL= 84 (63–94)
n=33, TV= 40 (32–44) n=33, HF= 9 (8–
10) n=32, E= 18 (16–20) n=38, TR= 11
(9–12) n=41, FA= 36.0 (34.2–38.5) n=43,
WT= 5.1 g (4.0–5.9) n=35.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3
similar species: Western Longeared
Myotis (Myotis evotis); see that
account for diagnostic traits.
range: restricted to the Pacific coast
where it ranges as far north as the Stikine
River on the mainland and Vancouver
Island and the Queen Charlotte Islands.

SPECIES ACCOUNTS 85
Myotis lucifugus (Little Brown Myotis)
description: the pelage varies from
nearly black in coastal populations to
tan or olive in the dry interior. The ears
reach the nostrils when pushed forward;
the calcar lacks a keel (Fig. 28).
The skull has a gradually sloped forehead
(Fig. 80).
External measurements: TL= 86 (70–108)
n=383, TV= 37 (25–59) n=379, HF= 10
(6–13) n=385, E= 13 (9–17) n=217, TR=
7 (4–10) n=151, FA= 36.4 (33.0–40.3)
n=295, WT= 6.2 g (3.0–10.2) n=98.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: the only Myotis species
with a similar ear size and lacking a keeled
calcar is the Yuma Myotis (M. yumanensis).
M. lucifugus has longer, glossier fur and is
generally larger (forearm >36 mm, skull length
>14 mm). The skull of M. lucifugus has a
more gradually sloping braincase than the
skull of M. yumanensis. Nonetheless, distinguishing
the two species is difficult in some
areas of the province with some individuals
intermediate in cranial and body size (see
Herd and Fenton 1983).
range: the largest
range of any British Columbian bat, inhabiting the
entire province including Vancouver Island and the
Queen Charlotte Islands.

86 SPECIES ACCOUNTS
Myotis septentrionalis
(Northern Long-eared Myotis)
description: a medium-sized
Myotis with long ears, dark fur, and no
shoulder patches. The outer edge of
the tail membrane is bare or with only
a few scattered hairs. The calcar lacks a
prominent keel (Fig. 28).
External measurements: TL= 86 (78–93)
n=3, TV= 37 (30–45) n=4, HF= 9 (8–10)
n=4, E= 17 (16–18) n=3, TR= 10 (10–
10) n=2, FA= 37.9 (35.6–40.0) n=3,
WT= 5.6 g (5.1–6.5) n=3.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: the Western
Long-eared Myotis (M. evotis), see that
species account for diagnostic traits.
range: known from Mount Revelstoke
National Park and north-eastern British
Columbia from the Peace River to the
Liard River area.

SPECIES ACCOUNTS 87
Myotis thysanodes (Fringed Myotis)
description: the largest Myotis
species in British Columbia, it has pale
brown fur, and long ears. The outer
edge of the tail membrane has a stiff
fringe of hairs that can be seen with the
naked eye (Fig. 25). The calcar is not
keeled (Fig. 28).
External measurements: TL= 90 (88–93)
n=7, TV= 42 (40–44) n=7, HF= 10 (8–
11) n=7, E= 19 (18–20) n=7, TR= 9 (8–
11) n=4, FA= 42.3 (40.0–44.5) n=38,
WT= 7.1 g (5.4–8.4) n=35.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: the only other
long-eared Myotis bat known to occur
within its range is the Western Long-eared
Myotis (M. evotis); see that species account
for diagnostic traits.
range: the Fraser, Okanagan, Thompson,
and Similkameen valleys of the dry interior
north to Williams Lake. Because there
are records from coastal regions of Oregon
and Washington State, M. thysanodes could
inhabit coastal regions of southwestern
British Columbia.

88 SPECIES ACCOUNTS
Myotis volans (Long-legged Myotis)
description: one of the largest Myotis
species in British Columbia, with hairs
on the belly that extend to the undersides
of the wing membranes as far as the
knees and elbows (Fig. 29). The ears are
more rounded in profile than any of our
other Myotis species. The calcar has a
prominent keel (Fig. 27). The skull has a
strongly elevated braincase (Fig. 77).
External measurements: TL= 94 (83–105)
n=33, TV= 43 (37–54) n=33, HF= 9 (7–10)
n=31, E= 12 (9–15) n=22, TR= 6 (5–7)
n=17, FA= 38.3 (34.0–43.0) n=46, WT=
7.2 g (5.5–10.0) n=18.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: there are only three bats
in British Columbia with prominent keels
that could be confused with this species: the
California Myotis (M. californicus), Western
Small-footed Myotis (M. ciliolabrum), and
Big Brown Bat (E. fuscus). M. californicus and
M. ciliolabrum are much smaller (forearm

SPECIES ACCOUNTS 89
Myotis yumanensis (Yuma Myotis)
description: the pelage varies from
nearly black in coastal populations to pale
brown in the dry interior. The pelage tends
to be dull and lacks a distinct sheen; the
calcar lacks a keel (Fig. 28). The skull has a
steeply sloped forehead (Fig. 79).
External measurements: TL= 82 (60–99)
n=322, TV= 36 (27–45) n= 324, HF= 9 (6–
13) n=323, E= 14 (8–16) n=202, TR= 7 (5–
10) n=212, FA= 34.3 (30.0–38.0) n=273,
WT= 6.6 g (4.0–8.5) n=153.
Dental Formula: incisors 2/3, canines 1/1,
premolars 3/3, molars 3/3.
similar species: the only similar species is
the Little Brown Myotis (M. lucifugus); see that
account for diagnostic traits.
range: Various coastal islands including
Vancouver Island, the coastal mainland north to
Kimsquit, and the interior
north to Williams Lake and
east to Nelson.

90 SPECIES ACCOUNTS
ORDER LAGOMORPHA: LAGOMORPHS
The tail is either “powder-puff” like or inconspicuous, soles of the feet are
furred, the front foot has five digits, and the hind foot has four digits. The
nostrils are surrounded by a rim of sparsely haired skin. The skull has a
fenestrate rostrum, two pairs of upper and one pair of lower incisors, no
canine teeth, and a space (diastema) that separates the incisors from the cheek
teeth. The cheek teeth are not rooted.
FAMILY OCHOTONIDAE: PIKAS
Small lagomorphs with short and nearly circular ears, the tail is not visible,
and the hind limbs are only slightly longer than front limbs. The skull is flat
with a short narrow rostrum that has a single oval fenestration (Fig. 83); there
are no supraorbital process (Fig. 82).
Ochotona collaris (Collared Pika)
description: the dorsal pelage is dull grey
with some buffy fur on the head and back. An
indistinct grey collar is present on the neck and
shoulders. The ventral pelage is white.
External measurements: TL= 197 (170–217)
n=18, HF= 32 (28–34) n=18, E= 22 (20–22)
n=7, WT= 146.7 g (123.0–173.0) n=7.
Dental Formula: incisors 2/1, canines 0/0,
premolars 3/2, molars 3/3
similar species: the only similar species is
the American Pika (O. princeps) but its distribution
is separated from that of O. collaris by a
hiatus of about 800 km in central British Columbia.
O. princeps can be distinguished by its brown
dorsal pelage that lacks a distinct collar, but the
two species overlap extensively
in skull and dental
measurements.
range: extreme north-western British Columbia
in the Haines Triangle and Bennett Lake region.

SPECIES ACCOUNTS 91
Ochotona princeps (Common Pika)
description: the dorsal fur colour is
extremely variable among the various subspecies
found in British Columbia, ranging
from pale grey or brown to blackish-brown
in coastal races. The species lacks a distinct
collar.
External measurements: TL= 178 (154–207) n=
456, HF= 31 (26–36) n=463, E= 21 (19–25)
n=65, WT= 162.3 g (142.5–190.4) n=18.
Dental Formula: incisors 2/1, canines 0/0,
premolars 3/2, molars 3/3
similar species: see account for the
Collared Pika (O. collaris).
range: northern limits are Kimsquit in the
Coast Mountains, the Itcha Mountains in
the Chilcotin region, Bowron Lakes Provincial
Park in the Cariboo Mountains, and
Mount Robson Provincial Park in the Rocky
Mountains. There are unconfirmed reports
of pikas from Ootsa
Lake and the Bulkley
Mountains in central
British Columbia.

92 SPECIES ACCOUNTS
FAMILY LEPORIDAE: HARES AND RABBITS
The ears are long, and the hind limbs have long feet. The skull is arched with
prominent supraorbital processes (Figs. 84, 86); the rostrum is long and wide
with lattice-like fenestrations (Fig. 85).
Lepus americanus
(Snowshoe Hare)
description: a medium-sized
hare with long ears. Except for
populations in the lower Fraser Valley
(i.e., subspecies washingtonii)
which remain brown all year, the
winter pelage is white with black
ear tips. Summer pelage is brown
but the dorsal surface of the hind
feet often remains white, and the
outer margins of the black-tipped
ears are white. In spring and autumn
the pelage is a mix of white
and brown. The skull has an indistinct interparietal bone (Fig. 86) and the
posterior extensions of the supraorbital processes are usually free of the
braincase (Fig. 86).
External measurements: TL= 443 (388–530)
n=139, TV= 39 (20–61) n=116, HF= 135
(117–155) n=133, E= 72 (64–95) n=49,
WT= 1.34 kg (0.89–1.92) n=12.
Dental Formula: incisors 2/1, canines 0/0,
premolars 3/2, molars 3/3.
similar species: throughout most
of the province this is the only species of
hare or rabbit. However, where its distribution
overlaps with the White-tailed
Jackrabbit (L. townsendii) and Nuttall’s
Cottontail (Sylvilagus nuttallii) in the
Okanagan Valley, and with the introduced
Eastern Cottontail (Sylvilagus
floridanus) in the Fraser River valley, identification
can be problematic.

SPECIES ACCOUNTS 93
L. townsendii is larger (ear >100 mm, basilar length of skull >69.0 mm,
maxillary toothrow length >16.0 mm) and has a silver-grey pelage. Cottontails
(S. floridanus and S. nuttallii) have smaller hind feet (

94 SPECIES ACCOUNTS
Lepus townsendii (White-tailed Jackrabbit)
description: a large hare with
long hind legs and very long, blacktipped
ears. In summer the dorsal
pelage is light grey mixed with pale
brown. In winter, the dorsal pelage
appears silvery-white washed with
brown. The skull is large with an
indistinct interparietal bone (Fig. 86),
broad rostrum, and supraoccipital
processes that usually touch the
braincase.
External measurements: TL= 564 (510–
602) n=11, TV= 90 (75–113) n=11,
HF= 150 (137–171) n=11, E= 120
(109–137) n=3, WT=2.54–2.56 kg
n=227 Dental Formula: incisors 2/1, canines 0/0,
premolars 3/2, molars 3/3
similar species: co-occurs with Nuttall’s
Cottontail (S. nuttallii) and the Snowshoe Hare
(L. americanus) in southern British Columbia
but L. townsendii can be readily identified by its
larger size especially the longer ears (>100 mm)
and larger skull (basilar length>69.0 mm, maxillary
toothrow length > 16.0 mm). L. americanus
turns white in winter, but its winter pelage is
nearly pure white rather than dirty silver-grey.
range: historically inhabited the southern Okanagan
and Similkameen valleys but probably extirpated.
27 No weights available for the historical British Columbian population, taken from Verts and
Carraway (1998).

SPECIES ACCOUNTS 95
Oryctolagus cuniculus (European Rabbit)
description: a medium to large rabbit
that is extremely variable in fur colour
(black to white) and markings depending
on the domestic breed. Brown individuals
have a rufous brown nape at the
dorsal base of the head (Fig. 33). The
skull has a distinct interparietal bone (Fig.
84) and the posterior extension of the
supraorbital processes are free of the
braincase.
External measurements: TL= 569 (500–620) n=4, TV= 70 (55–85) n=4, HF= 112
(102–121) n=5, E= 116 (84–152) n=5, WT= 3.26 kg (2.90–3.95) n=4.
Dental Formula: incisors 2/1, canines 0/0,
premolars 3/2, molars 3/3
similar species: most breeds have distinctive
colour and markings (ranging from
black to white) that readily distinguish them
from our wild rabbits and hares. However,
brown O. cuniculus could be confused with the
Snowshoe Hare (L. americanus) or cottontail
species (S. floridanus and S. nuttallii). O. cuniculus
is larger (total length >490 mm), more
heavily built, and has longer ears (> 80 mm)
than cottontails (Sylvilagus); the brownish nape
and heavier build will discriminate O. cuniculus
from L. americanus in summer pelage. The
skull of O. cuniculus can be discriminated from that of L. americanus by its
distinct interparietal bone. Cottontail (Sylvilagus) skulls have a distinct
interparietal but the tip of the posterior extension of their supraorbital
processes touch the braincase.
range: generally a domestic mammal but
feral populations occur on Triangle Island.
Localized feral populations periodically appear
in other parts of the province but they
rarely persist.

96 SPECIES ACCOUNTS
Sylvilagus floridanus (Eastern Cottontail)
description: a medium-sized
rabbit with brownish pelage and a
rufous or brownish nape on the
back of the head (Fig. 33). The ears
are black-tipped; the ventral pelage
is white. The skull has a distinct
interparietal bone (Fig. 84) and
supraoccipital processes that touch
the braincase.
External measurements: TL= 423 (370–449)
n=31, TV= 51 (35–70) n=31, HF= 99 (90–110)
n=31, E= 68 (61–76) n=14, WT= .33 kg (1.11–
1.72) n=32.
Dental Formula: incisors 2/1, canines 0/0,
premolars 3/2, molars 3/3
similar species: could be confused with
Snowshoe Hares (L. americanus) in summer
pelage and with brown forms of O. cuniculus
(see those accounts for diagnostic traits).
range: two introduced populations occur in British
Columbia: a lower Fraser River valley population that
is derived from introductions to western Washington
and a population recently introduced to Vancouver
Island.

SPECIES ACCOUNTS 97
Sylvilagus nuttallii (Nuttall’s Cottontail)
description: our smallest
rabbit, it has a dorsal pelage characterized
by pale brown fur with
grey on the sides and rump, and
a pale brown nape (Fig. 33). The
ears are tipped with black. The
ventral pelage is white. The skull
is small with a distinct interparietal
bone (Fig. 84) and
supraoccipital processes that
touch the braincase.
External measurements: TL= 319 (263–363) n=9,
TV= 33 (24–44) n=9, HF= 85 (75–90) n=9, E= 57
(54–58) n=4, WT= 495.4 g (341.9–777.5) n=4.
Dental Formula: incisors 2/1, canines 0/0,
premolars 3/2, molars 3/3
similar species: in British Columbia, the
distributions of the Eastern Cottontail (S.
floridanus) and Nuttall’s Cottontail (S. nuttallii)
are not in contact. But, S. nuttallii can be discriminated
from S. floridanus by smaller body
size (weight< 700 g, ear 57 mm, maxillary toothrow
length >14 mm).
range: the southern Okanagan and Similkameen
valleys.

98 SPECIES ACCOUNTS
ORDER RODENTIA: RODENTS
The external appearance is diverse with the anatomy of some species highly
modified for specializations associated with locomotion. The skull is characterized
by a single pair of upper incisors, no canines, the incisors separated
from cheek teeth by a space, and the rostrum lacking fenestrations. All British
Columbia rodents have rooted cheek teeth, except for some species of voles,
the Mountain Beaver (Aplodontia rufa), and Northern Pocket Gopher
(Thomomys talpoides) which have ever-growing cheek teeth.
FAMILY APLODONTIDAE: MOUNTAIN BEAVERS
Aplodontia rufa (Mountain Beaver)
description: a thickset rodent
with dark brown fur, short limbs, an
indistinct stubby tail, small eyes and
ears, and long claws on the front
feet. The skull is flattened, and triangular
in outline with flask-shaped
auditory bullae (Fig. 129), no postorbital
processes, and molars with
distinct projections on their cheek sides.
External measurements: TL= 349 (260–470)
n=88, TV= 27 (17–47) n=72, HF= 57 (48–
68) n=77, E= 20 (16–22) n=5, WT= 1.05
(0.67–1.30) n=7.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3.
similar species: none, but curiously,
young marmots (Marmota) have been
misidentified as A. rufa. Marmots have a
bushy tail and short claws.
range: southwestern British Columbia in the
Cascade Range and lower Fraser River valley.

SPECIES ACCOUNTS 99
FAMILY SCIURIDAE: SQUIRRELS
Species typically have a bushy tail and dense fur. There are four toes on the
front feet and five on the hind feet. Some species have internal cheek pouches.
The skull has pronounced postorbital processes, a wide interorbital area, and
a small infraorbital opening (Fig. 90).
Glaucomys sabrinus (Northern Flying Squirrel)
description: a medium-sized squirrel with a broad flat tail, large dark
eyes bordered by a black ring, and a fold of skin that forms a gliding membrane
extending along the sides between
the wrist and ankle. The soft silky
dorsal pelage varies from greybrown
to rich brown; the undersides,
which are separated from the
dorsal fur by a distinct dark lateral
line, are pale with hairs that are
grey at the base and whitish or tan
at the tips. The skull has a distinct V-shaped notch in the interorbital region
(Fig. 142), an inflated braincase, and postorbital processes that taper to a
sharp point.
External measurements: TL= 322 (298–344) n=51,
TV= 144 (130–164) n=51, HF= 42 (39–46) n=50,
E= 21 (17–25) n=50, WT= 155.5 (124.0–200.6)
n=58.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: none.
range: entire mainland and some coastal
islands (but not Vancouver Island).

100 SPECIES ACCOUNTS
Marmota caligata (Hoary Marmot)
description: a large marmot with a distinct dorsal pelage that is white to
grey with a dark wash in the shoulder region giving it a mantled appearance.
The head has a white nose and black
cap that extends to the side of
the face; the dorsal surfaces of
the hind feet are black.
Melanic individuals occur
in some coastal populations.
The posterior pad on
the sole of the hind foot is
circular in shape (Fig. 40).
The skull is straight in dorsal
profile (Fig. 132) with a distinct depression in the interorbital region. The
postorbital processes are oriented at right angles to the main axis of skull (Fig.
133); the posterior border of the nasal bones
is square or arched (Fig. 137).
External measurements: TL= 673 (505–800)
n=102, TV= 199 (140–246) n=106, HF= 94
(78–112) n=101, E= 26 (19–32) n=11, WT=
4.59 kg (3.09–5.59) n=6.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: the Yellow-bellied
Marmot (Marmota flaviventris) and Woodchuck
(Marmota monax) lack the hoary
colour pattern and have smaller skulls (maxillary
toothrow length

SPECIES ACCOUNTS 101
Marmota flaviventris (Yellow-bellied Marmot)
description: a small marmot with a brown dorsal pelage
that is grizzled with tan and grey. The ventral pelage is
tan to yellow. The head is black with a white or tan
area in front of eyes. The side of the neck is a
uniform pale yellow or tan that contrasts from the
sides and back. The dorsal surface of the
hind feet are yellow to tan. The posterior
pad on sole of the hind foot is
oval in shape (Fig. 39). The skull is
straight in dorsal profile with a distinct depression in the interorbital region;
the postorbital processes are positioned at right angles to the main axis of the
skull. The posterior border of the nasal bones forms an arch (Fig. 137) and the
upper toothrows diverge anteriorly.
External measurements: TL= 517 (415–660) n=37,
TV= 147 (103–184) n=39, HF= 72 (63–83) n=38,
E= 27 (23–33) n=4, WT28 = 1.5–3.7 kg n=9
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: to discriminate from M.
caligata see that account. Its range is mostly
separate from that of the Woodchuck
(Marmota monax) but the two marmots may
co-occur in the Chilcotin and northern Fraser
River valley region. M. monax lacks the white
markings on the face and light patches on the
side of the neck; its ventral fur is reddish-brown, and the dorsal surface of its
feet are dark brown. The skull of M. monax has parallel upper toothrows and
the posterior borders of the nasal bones form a V-shaped notch (Fig. 136).
range: the Fraser and Thompson Plateaus, and southern
mountains including the Cascade, Monashee, and
Selkirk mountains. Western limits of the range are the
east side of the Fraser River; northern limits are the
Williams Lake area although an historical museum
specimen was taken in the 1950s near
Prince George.
28 No weights available for British Columbian populations, taken from Verts and Carraway (1998).

102 SPECIES ACCOUNTS
Marmota monax (Woodchuck)
description: a small
marmot with brown dorsal
fur grizzled with silver grey
and reddish-brown ventral
pelage. The side of the neck
does not contrast from the sides
and back. The head is dark brown
with no white markings on the face.
The dorsal surface of the hind feet is dark brown
to nearly black. Populations in northern and south-eastern
British Columbia demonstrate a high incidence of melanism.
The posterior pad on the sole of the hind foot is oval in shape. The
skull is straight in dorsal profile with a distinct depression in the
interorbital region; the postorbital processes are at right angles to the main
axis of the skull. The posterior border
of the nasal bones forms a V-shaped notch
(Fig. 136); the upper toothrows are parallel.
External measurements: TL= 496 (388–597)
n=45, TV= 126 (98–171) n=44, HF= 72 (58–
81) n=49, E= 28 (25–31) n=5, WT= 1.59 kg
(1.06–2.40) n=7.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: Hoary Marmot
(M. caligata) and Yellow-bellied Marmot
(M. flaviventris); see those accounts for distinguishing
traits.
range: the Columbia Mountains, southern Rocky
Mountains and most of the central and northern
interior. It is generally absent from coastal
regions, although there are records from the Skeena
River and Stikine River valleys in the Coast
Mountains.

SPECIES ACCOUNTS 103
Marmota vancouverensis
(Vancouver Island Marmot)
description: a large marmot
with grizzled brown to black
pelage, a white nose, and white
markings on the forehead, chin
and belly. Old faded fur is much
paler ranging from tan to light brown.
The posterior pad on the sole of the
hind foot is round in shape. The skull is
straight in dorsal profile, the interorbital region has a distinct depression, and
the postorbital processes are at right angles to the main axis of the skull. The
posterior border of the nasal bones forms a V-shaped notch (Fig. 136).
External measurements: TL= 668 (580–750)
n=23, TV= 200 (162–300) n=23, HF= 97
(80–105) n=22, E= 29 (24–35) n=13, WT=
3.76 kg (3.20–4.40) n=3.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: the fur colour resembles
that of melanic hoary marmots
(M. caligata) but the two species do not
overlap in their distributions.
range: confined to south-central Vancouver
Island.

104 SPECIES ACCOUNTS
Sciurus carolinensis (Eastern Grey Squirrel)
description: a large tree squirrel with a long
bushy tail that exhibits three distinct colour
phases: grey, intermediate, and black. The grey
morph has a grey dorsal pelage with a red or
cinnamon tinge; the ventral pelage is white.
There are patches of white hairs behind the
ears, and the tail is edged with long white hairs.
The intermediate and black morphs are
two forms of melanism with the black
morph pure black and the intermediate
morph a brownish colour that results
from reddish-brown or blonde bands in the
fur. All three colour morphs occur in southwestern
British Columbia with melanism (black,
intermediate morphs) the dominant pelage
colour in the lower Fraser Valley population,
whereas the south-eastern Vancouver Island
population consists almost entirely of the grey
morph. The skull has parallel zygomatic arches
that are not flattened in a horizontal plane (Fig.
141); the ventral border of the orbit is opposite
the first upper molar (Fig. 143). Most individuals
have two upper premolars but the first tiny
peg-like premolar may be missing in some individuals.
External measurements: TL= 476 (425–526) n=21, TV= 216 (186–250) n=21, HF=
67 (60–72) n=22, E= 28 (23–32) n=19, WT= 534.8 g (309.3–700.6) n=21.
Dental Formula: incisors 1/1, canines 0/0, premolars 2/1, molars 3/3
similar species: although it resembles the Fox Squirrel (Sciurus niger),
another introduced species, distributions of the two species are widely separated
in British Columbia. S. niger is distinguished by its yellow-orange
ventral pelage, reddish-orange ear tufts; one pair of upper premolars.
range: there are two introduced populations
in the province. A population in the lower
Fraser valley originated from an introduction
to Stanley Park in the 1920s and a population
in the Victoria region of Vancouver Island
that was introduced in the 1960s.

SPECIES ACCOUNTS 105
Sciurus niger (Eastern Fox Squirrel)
description: a large tree squirrel with a long bushy tail. Many colour
morphs occur in eastern North America, but only the typical colour morph
with a grey dorsal pelage washed with light orange
or tan occurs in British Columbia. The ventral
pelage is whitish with a pale orange wash.
There are patches of orange or tan hairs
behind the ears. The dorsal surface of the
tail has tricoloured hairs that are tan at
their base, black in their mid section,
and orange at the distal end. The underside
of the tail is deep orange. The
skull has parallel zygomatic arches that
are not flattened in a horizontal plane;
the ventral border of the orbit is opposite
first upper molar.
External measurements: TL= 454 (417–480) n=3,
TV= 203 (201–204) n=3, HF= 65 (62–67) n=3, E=
22 (18–27) n=3, WT= 529.8 (529.6–530.0) n=2.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/1, molars 3/3
similar species: the Eastern Gray Squirrel
(S. carolinensis); see that account for distinguishing
traits.
range: extreme southern
Okanagan Valley
where it ranges from
Osoyoos to Okanagan
Falls. This population presumably originated from
populations introduced to Washington State.

106 SPECIES ACCOUNTS
Spermophilus columbianus (Columbian Ground Squirrel)
description: the dorsal fur is grey washed
with brown, and has a spotted or mottled
pattern with brownish spots. The side of
the neck is greyish, and the nose and
front of the head are orange-brown.
The underside of the tail is a mix of
black and white. The hind legs and
dorsal surface of the feet are reddishbrown.
The skull is convex in dorsal
profile (Fig. 134), with the zygomatic
arches converging anteriorly in a
horizontal plane (Fig. 140).
External measurements: TL= 341 (280–395)
n=164, TV= 97 (78–120) n=161, HF= 51 (42–
59) n=163, E= 16 (10–24) n=52, WT= 421.4 g
(195.0–625.0) n=35.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: the only other British
Columbia ground squirrel with similar pelage
colour and markings and skull
morphology is the Arctic Ground Squirrel
(Spermophilus parryii). Their ranges are separated
by about 300 kilometres in British
Columbia. Nevertheless, S. parryii can be
discriminated by paler fur on the side of its
neck and undersides of the tail and white spots in the mid dorsal area white.
Skulls of the two species overlap considerably in size and they cannot be
discriminated by any single measurement.
range: the southern interior as far north as Intersection
Mountain north of the Yellowhead Pass in the
Rocky Mountains and Bowron Lake Provincial Park in
the Cariboo Mountains. Western limits of its range
are in the Cascade Mountains, and the east side of
the Fraser River in the dry interior.

SPECIES ACCOUNTS 107
Spermophilus lateralis (Golden-mantled Ground Squirrel)
description: the dorsal pelage has two
longitudinal white stripes, each bordered
by a pair of black stripes. The four dark
stripes are complete and contrast sharply
with the white stripes (Fig. 37). The stripes
do not extend onto the head. A conspicuous
rusty-red mantle is usually present on
the head and shoulders, although in some
individuals it may be indistinct. The ventral pelage is creamy
white. The underside of the tail is pale yellow; the dorsal surface of the hind
feet is pale yellow to nearly white. The skull is convex in dorsal profile; the
zygomatic arches converge anteriorly in a horizontal plane .
External measurements: TL= 268 (171–360) n=114,
TV= 97 (70–132) n=113, HF= 43 (35–55) n=114, E=
17 (12–23) n=30, WT= 196.8 g (165.0–216.7) n=10.
Dental Formula: incisors 1/1, canines 0/0, premolars
2/1, molars 3/3
similar species: chipmunks (Tamias) have
five dark stripes and four light stripes , their body
stripes extend onto the head, and they are smaller
(skull length 10.0 mm).
Although their distributions are not known to overlap in British Columbia,
this species is similar to the Cascade Mantled Ground Squirrel (Spermophilus
saturatus). Externally, S. saturatus can be discriminated by: darker and duller
pelage than S. lateralis, a dull indistinct mantle, a poorly defined inner-most
dark stripe, and dark stripes that do not contrast sharply from the whitish
stripe. The skull of S. saturatus averages slightly larger than that of S. lateralis
but all measurements overlap among the two species.
range: the Monashee, Selkirk, Purcell, Cariboo, and
Rocky mountains where it ranges as far north as Mount
Selwyn and Bowron Lakes Provincial Park. Western
limits of its range are the Okanagan Valley on the
east side of Okanagan Lake.

108 SPECIES ACCOUNTS
Spermophilus parryii (Arctic Ground Squirrel)
description: the dorsal fur is grey washed with
brown, and has a spotted or mottled pattern with
whitish or tan spots. The side of the neck is
tawny brown; the nose and front of the
head is orange-brown. The underside of
the tail is reddish with a black tip;
the hind legs and dorsal surface
of the feet are grey to yellowishbrown.
The skull is convex in
dorsal profile; the zygomatic
arches converge anteriorly in a
horizontal plane.
External measurements: TL= 332 (300–375)
n=84, TV= 87 (72–111) n=99, HF= 52 (45–57)
n=96, E= 15 (9–18) n=8, WT= 462.8 g (350.0–
557.0) n=14.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: see the account for the
Columbian Ground Squirrel (S. columbianus).
range: north-western British Columbia
from the Haines Triangle through the Cassiar
Mountains and the Skeena Mountains as far
south as Tatlatui Lake near the headwaters of
the Finlay River. It has
not been recorded in
the northern Rocky
Mountains.

SPECIES ACCOUNTS 109
Spermophilus saturatus
(Cascade Mantled Ground Squirrel)
description: the dorsal pelage
has two longitudinal white or
tan stripes, each bordered by
a pair of indistinct black
stripes. The body stripes do
not extend onto the head. A
dull, poorly defined mantle of
brown or reddish fur is present
on the head and shoulders
(Fig.38). In some individuals the
mantle is absent. The ventral pelage is
tan or pale brown. The dorsal surface of
the hind feet are tan; the underside of the tail is yellow to light orange. The
skull is convex in dorsal profile; the zygomatic arches converge anteriorly in
a horizontal plane.
External measurements: TL= 300 (253–320)
n=30, TV= 103 (89–115) n=29, HF= 46 (40–
53) n=30, E= 22 (21–23) n=3, WT= 245.0 g
(162.0–314.0) n=3.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: closely resembles the
Golden-mantled Ground Squirrel (S. lateralis);
see its account for diagnostic traits.
range: the Cascade
Range of southwestern
British Columbia.

110 SPECIES ACCOUNTS
Tamias amoenus
(Yellow-pine Chipmunk)
description: the dorsal pelage has five
dark and four light stripes, with the middle
dark stripe extending from back of the
head to the rump and the other dark
stripes extending from the side of head to
the rump. Typically this species is brightly
coloured with yellow-brown sides, a buff
belly, and the underside of
the tail yellow to
orange. However,
T. amoenus is the
most variable of any
of our chipmunks, and the five subspecies found in the province demonstrate
pronounced colour variation, ranging from rich brown in coastal forms
(T. a. felix) to pale grey in the dry interior (T. a. affinis). The skull has a simple
rounded infraorbital opening piercing the zygomatic plate (Fig. 138). The
baculum is small (shaft length 2.2 to 2.7 mm) with a tip length more than 30%
of the shaft length. The baubellum is small (greatest length 1.0 to 1.8 mm) with
a short indistinct base that may be notched in some specimens (Fig. 148).
External measurements: TL= 213 (198–230)
n=58, TV= 94 (79–110) n=58, HF= 32 (28–
34) n=61, E=16 (11–18) n=47, WT= 55.0
(42.0–77.0) n=50.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: the distribution
overlaps with the three other chipmunks
in British Columbia: Least Chipmunk
(Tamias minimus), Red-tailed Chipmunk
(Tamias ruficaudus), and Townsend’s
Chipmunk (Tamias townsendii).
T. townsendii is easily distinguished by its
dull, indistinct light stripes, frosted tail,
and larger size (body length >130 mm,
skull length > 37.0 mm, maxillary
toothrow length > 6.0 mm).

SPECIES ACCOUNTS 111
In the Purcell Mountains and southern Rocky Mountains of south-eastern
British Columbia, T. minimus is smaller (total length less

112 SPECIES ACCOUNTS
Tamias minimus (Least Chipmunk)
description: generally greyish-brown in fur
colour with a grey rump, white belly, and yellow
on the neck, sides, and underside of the tail.
The striping pattern consists of the typical
chipmunk pattern of five dark and four light
stripes. Populations in south-eastern British
Columbia (i.e., the subspecies T. m. oreocetes
in the southern Rockies and T. m. selkirki in
the Purcell Mountains) tend to be
smaller and paler than northern
populations. The skull has a simple
rounded infraorbital
opening piercing the
zygomatic plate; it is the smallest
skull of any chipmunk in the province. The baculum is small (shaft length 2.6
to 2.9 mm) with a tip that is less than 30% of the shaft length). The baubellum
is small (greatest length 0.9 to 1.1 mm) with a distinct “U” shaped base that
tapers sharply at its proximal end (Fig. 147).
External measurements: TL= 198 (172–222)
n=78, TV= 87 (69–101) n=79, HF= 31 (27–
34) n=85, E= 13 (10–16) n=75, WT=45.5
(36.0–62.0) n=76.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: its distribution overlaps
with T. amoenus and T. ruficaudus. See
the account for T. amoenus for diagnostic
traits. T. ruficaudus is easily discriminated
by its larger size (total length greater than
205 mm; skull length greater than 34.0 mm)
and darker pelage
with rufous on the sides and underside of the tail.
range: northern British Columbia south to the
Peace River and Babine Lake region. In central
and southern parts of the province it is restricted
to the Rocky Mountains and the Purcell
Mountains.

SPECIES ACCOUNTS 113
Tamias ruficaudus (Red-tailed Chipmunk)
description: a large chipmunk with the typical striping pattern of five
dark and four light stripes. Size and pelage varies strikingly among the two
subspecies. The Rocky Mountain population
(i.e., T. r. ruficaudus) has bright reddish pelage
on the underside of the tail and the sides
and back of the head are washed with
yellow. In contrast, the Selkirk
Mountains form (i.e., T. r. simulans)
is paler with tan or yellow fur on the
underside of the tail. The skull has a
simple rounded infraorbital opening
piercing the zygomatic plate. The
baculum and baubellum are large and
robust (shaft length of the baculum
3.4 to 4.7 mm, greatest length of the
baubellum 2.0 to 3.2 mm).
External measurements: TL= 223 (207–237)
n=47, TV= 991 (89–115) n=46, HF= 33 (30–
35) n=46, E= 17 (13–19) n=37, WT=59.5 g
(44.2–78.7) n=37.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: see accounts for the
Yellow-pine Chipmunk (T. amoenus) and
Least Chipmunk (T. minimus) for identification
problems.
range: two disjunct
populations occur in
British Columbia. One is restricted to the southern
Selkirk Mountains where its range is delimited by
the Kootenay and Columbia rivers. Another population
inhabits the southern Rocky Mountains
ranging from the Akamina Pass-Wall Lake
area as far north as Middle Kootenay Pass.

114 SPECIES ACCOUNTS
Tamias townsendii (Townsend’s Chipmunk)
description: a large chipmunk
with a rich brown pelage and
the typical chipmunk
striping pattern although
the four light stripes tend
to be indistinct. White or
grey patches occur behind
the ears. The fur on the
dorsal surface of the tail has
a frosted appearance resulting
from black hairs tipped
with silver-grey. The colour
varies geographically, with the coastal subspecies (T. t. townsendii) very dark
with indistinct light stripes and the Cascade Mountain subspecies (T. t.
cooperi) paler with the light stripes contrasting more with the dark stripes. The
skull has a simple rounded infraorbital opening
piercing the zygomatic plate; it is the largest
skull of any British Columbia chipmunk. The
baculum is small (shaft length 2.2 to 2.6 mm)
with the tip length more than 30% of the shaft
length. The baubellum is small (greatest length
about 1.0 mm) with a “U” shaped base that
tapers sharply at its proximal end.
External measurements: TL= 260 (234–286) n=43,
TV= 114 (103–130) n=43, HF= 36 (32–40) n=42,
E= 19 (17–23) n=12, WT= 77.8 (65.2–89.0) n=11.
Dental Formula: incisors 1/1, canines 0/0,
premolars 2/1, molars 3/3
similar species: T. amoenus is the only chipmunk species that overlaps
with the range of T. townsendii; see that account
for diagnostic traits.
range: extreme southwestern British Columbia
in the lower Fraser Valley and
Cascade Range east to Allison Pass and
Treasure Mountain.

SPECIES ACCOUNTS 115
Tamiasciurus douglasii (Douglas’ Squirrel)
description: a small tree squirrel with an olive-brown dorsal pelage and
ventral pelage that ranges from pale yellow to orange. The tail hairs are tipped
with white or pale yellow.
The skull has the infraorbital
opening modified as a canal that
passes between the zygomatic
plate and the side of the rostrum
(Fig. 139), the zygomatic
arches are parallel and not
flattened in a horizontal plane
(Fig. 141). The anterior border
of the orbit is opposite the second
upper premolar (Fig. 143).
External measurements: TL= 308 (271–351) n=144, TV= 122 (90–150) n=144, HF=
49 (44–57) n=125, E= 26 (20–31) n=151, WT= 203.5 g (157.4–270.6) n=154.
Dental Formula: incisors 1/1, canines 0/0, premolars 1/1, molars 3/3
similar species: the only similar species
is the Red Squirrel (Tamiasciurus hudsonicus)
which overlaps with T. douglasii along the
crest of the Cascades and southern Coast
Mountains. T. hudsonicus is generally discriminated
by its grey to olive-brown dorsal
pelage, white to grey belly, and tail hairs
tipped with red. Although T. hudsonicus is
larger, the two species overlap extensively in
their skull and body measurements. Identification
is problematic in parts of the Cascade
Mountains (Manning Provincial Park, Fraser
River canyon) where some squirrels appear
intermediate in pelage,
vocalizations, and skull morphology (see Smith 1981).
range: Fraser Valley, Cascade Range and the Coast
Mountains north to Rivers Inlet.

116 SPECIES ACCOUNTS
Tamiasciurus hudsonicus
(Red Squirrel)
description: a small tree squirrel
with an olive-brown dorsal pelage and
undersides that range from white to
grey. The tail hairs are tipped
with red. The skull has an
infraorbital opening modified
as a canal that passes between
the zygomatic plate and the
side of the rostrum. The
zygomatic arches are parallel
and not flattened in a horizontal
plane; the anterior border of the orbit
is opposite the second upper premolar.
External measurements: TL= 318 (192–363)
n=342, TV= 125 (99–150) n=342, HF= 49
(32–57) n=328, E= 25 (14–32) n=328,
WT= 224.5 (147.8–295.2) n=365.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/1, molars 3/3
similar species: in some parts of the
Cascades and Coast Mountains can be
confused with T. douglasii; see that account
for diagnostic traits.
range: the entire
mainland excluding
southwestern British
Columbia and Vancouver Island;
introduced to the Queen Charlotte Islands.

SPECIES ACCOUNTS 117
FAMILY GEOMYIDAE: POCKET GOPHERS
Thomomys talpoides
(Northern Pocket Gopher)
description: a chipmunk-sized
rodent with a thickset body, short
legs and tail, and small eyes and
ears. The front feet have five strong
claws. Two fur-lined cheek
pouches extend from the face to the
shoulder area (Fig. 41). The dorsal pelage is
generally brown, although melanic individuals occur in some populations.
Some populations have prominent white markings on the chin, forearms, and
abdomen. The skull is flattened with wide zygomatic arches and an infraorbital
foramen positioned on the side of the rostrum in front of the zygomatic plate.
The upper and lower premolars are indented on the side forming an “8” shape
(Fig. 130).
External measurements: TL= 199 (154–230) n=413,
TV= 26 (22–36) n=228, HF=26 (22–36) n=228, E= 5
(4–7) n=17, WT= 90.7 g (69.1–113.0) n=24 males;
83.2 g (60.8–116.4 ) n=31 females.
Dental Formula: incisors 1/1, canines 0/0, premolars
1/1, molars 3/3
similar species: none.
range: southern interior of British Columbia
from the east Kootenays to the east slopes of the
Cascade Range and north to
the south side of the
Thompson River.

118 SPECIES ACCOUNTS
FAMILY HETEROMYIDAE: HETEROMYIDS
Perognathus parvus
(Great Basin Pocket Mouse)
description: a ‘mouse-like’
rodent with a long tail (greater
than head and body length),
small ears, and external furlined
cheek pouches. The
dorsal pelage is dull greybrown
and the undersides are
white. The skull has a large
circular infraorbital opening on
the side of the rostrum (Fig. 91),
and slender zygomatic arches. The incisors are thin and compressed.
External measurements: TL= 175 (151–202)
n=241, TV= 93 (77–112) n=238, HF= 23
(20–27) n=237, E= 6 (4–10) n=55, WT=
19.7 g (16.0–28.0) n=32.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/1, molars 3/3
similar species: the Deer Mouse
(Peromyscus maniculatus) is the only
rodent that could be confused with this
species. P. maniculatus has larger ears, a
shorter tail, and no cheek pouches; its
skull has a V-shaped infraorbital opening
at the base of the zygomatic arch (Fig. 92)
and only three pairs of cheek teeth
(no premolars).
range: the dry interior grasslands of British Columbia
in the Okanagan, Similkameen, Kettle, and
Thompson valleys.

SPECIES ACCOUNTS 119
FAMILY CASTORIDAE: BEAVERS
Castor canadensis (Beaver)
description: our largest rodent with
webbed hind feet, a flat scaly tail, and
long glossy guard hairs. The skull
is massive with high crowned
cheek teeth, large incisors, and
a prominent depression in
the basioccipital region
(Fig. 131).
External measurements:
TL= 1041 (900–1212)
n=58, TV= 297 (146–500) n=54, HF= 175
(146–200) n=57, E= 35 (30–44) n=41,
WT= 19.2 kg (11.6–35.3) n=43.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/1, molars 3/3
similar species: none.
range: the entire mainland and
many coastal islands including Vancouver
Island; introduced to the Queen
Charlotte Islands.

120 SPECIES ACCOUNTS
FAMILY MURIDAE: RATS, MICE, VOLES, LEMMINGS
Although their external appearance is variable most species tend to be ‘mouse
or rat-like’; the skull has three upper and three lower pairs of cheek teeth and
a V-shaped infraorbital foramen (Fig. 92). Three subfamilies are represented
in British Columbia.
Subfamily Arvicolinae: Voles and Lemmings
Stocky rodents with a blunt muzzle, small eyes and ears, relatively short legs,
and a tail that is usually shorter than the head and body length (Fig. 43). The
skull is angular in profile. The crowns of the molars have prisms arranged in
alternating triangles (Fig. 88). In the Muskrat (Ondatra zibethicus), Redbacked
Voles (Clethrionomys) and Heather Vole (Phenacomys intermedius)
the molars are rooted; but are ever-growing in other species.

SPECIES ACCOUNTS 121
Clethrionomys gapperi (Southern Red-backed Vole)
description: a small vole with long and
thick dorsal fur with a rufous-brown or chestnut
median stripe that extends from the head
to the rump. The ventral pelage is white to
grey; the hind feet are dark grey or black
washed with silver. The dorsal stripe may be
inconspicuous in young animals. The tail,
which is 22-32 % of the total length, is slender
and sparsely furred with grey or white hairs on
the ventral surface. A dark colour phase found in some northern populations
has a grey or black dorsal stripe, grey sides, and a dark tail. The rounded
delicate skull has small rooted cheek teeth and a palate that terminates
posteriorly in a simple transverse shelf (Fig. 106) in which the posterior edge
is usually completely fused (Fig. 108).
External measurements: TL= 133 (110–162)
n=597, TV= 36 (22–55) n=596, HF= 18 (14–
22) n=597, E= 14 (9–19) n=512, WT= 22.9
(15.0–45.0) n=597.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3
similar species: identification may be
problematic in northern British Columbia
where this species overlaps in its distribution
with the Northern Red-backed Vole
(Clethrionomys rutilus). Adult C. rutilus have
a more densely furred and thicker tail that is
yellow on the ventral surface. The skull of C.
rutilus is discriminated from that of C. gapperi by a palate that is incompletely
fused at its posterior edge (Fig. 109). Nevertheless, Bee and Hall (1956)
reported that the fusion of the palate was related to
growth and age. Some old adult C. rutilus may have
complete palates and the palate may not be completely
fused in some immature C. gapperi.
range: found across most of the province except
the extreme northwest where it is replaced by the
Northern Red-backed Vole. It also occurs on
several central coast islands.

122 SPECIES ACCOUNTS
Clethrionomys rutilus
(Northern Red-backed Vole)
description: a small vole with
a rufous-brown or chestnut median
stripe on its back. The dorsal
fur is long and thick; the undersides
are white to grey. The tail
which is 19–30 % of the total
length is thick and densely furred
with yellow fur on its ventral surface.
The skull has small rooted
cheek teeth; the palate terminates posteriorly in a simple transverse shelf with
the posterior edge of the palate incompletely fused (Fig. 109).
External measurements: TL= 129 (110–148)
n=85, TV= 31 (21–41) n=104, HF= 19 (15–21)
n=103, E= 14 (11–17) n=37, WT= 25.4 g (18.0–
31.8) n=25.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3
similar species: C. rutilus may be
confused with the Southern Red-backed
Vole (C. gapperi); see that account for
identification.
range: extreme
north-western part of
the province from the Haines Triangle east to the
northern Rocky Mountains and as far south as
Spatsizi Plateau.

SPECIES ACCOUNTS 123
Lemmus trimucronatus (Brown Lemming)
description: a large stocky vole with
long, soft fur; and bright orange-brown
dorsal pelage. The tail is short (

124 SPECIES ACCOUNTS
Microtus longicaudus (Long-tailed Vole)
description: a medium-sized vole
with a long tail 30 to 44% of its total
length. The Goose Island population
demonstrates gigantism
with some adults more than
60 g. The dorsal pelage ranges
from dull grey or reddish brown
to nearly black in some coastal
populations. The undersides are
greyish. The skull is characterized
by a broad incisive foramen
with a sharply tapered anterior region, and incisors that do not protrude
beyond the nasal bones when the skull is viewed dorsally (Fig. 118). The
second upper molar lacks a posterior loop (Fig. 111), the third upper molar
has four inner salient angles (Fig. 115), and the first lower molar has five or six
closed triangles (Fig. 113).
External measurements: TL= 182 (150–267)
n=632, TV= 66 (50–90) n=622, HF= 21
(16–27) n=627, E= 13 (8–21) n=139, WT=
43.7 g (20.0–85.0) n=146.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: the distribution of
M. longicaudus overlaps with six other
Microtus species in British Columbia:
Creeping Vole (Microtus oregoni),
Meadow Vole (Microtus pennsylvanicus),
Montane Vole (Microtus montanus),
Townsend’s Vole (Microtus townsendii),
Tundra Vole (Microtus oeconomus), and
Water Vole (Microtus richardsoni). In external appearance, M. longicaudus
can be discriminated from most of these species by a relatively longer tail (tail
length> 50 mm and usually >33% of the total length). M. richardsoni has a
long tail but it can be distinguished from M. longicaudus by its longer foot
(hind foot> 28 mm) and larger adult body size (weight >90 g).
The skulls of M. oeconomus, M. pennsylvanicus, and M. oregoni can be
discriminated from M. longicaudus by their different molar enamel patterns
(see those accounts). M. richardsoni has the same molar enamel patterns but

SPECIES ACCOUNTS 125
its skull is much larger (maxillary toothrow length >7 mm). M. montanus and
M. townsendii also share the same molar enamel patterns and their skulls are
similar in size. Authorities such as Maser and Storm (1970) reported that
these species differ from M. longicaudus in having incisors that protrude
beyond the nasal bones when their skulls are viewed dorsally and incisive
foramen are that are narrow and not tapered anteriorly. Nevertheless, these
traits are variable and age-related; distinguishing their skulls from M.
longicaudus is difficult.
range: the entire British Columbian mainland and
various near shore coastal islands.

126 SPECIES ACCOUNTS
Microtus montanus (Montane Vole)
description: a small vole with grizzled-grey
or “salt and pepper” dorsal
pelage; the undersides are grey to
white. The fur on the dorsal surface
of the feet is silver-grey. The tail is
less than 30% of the total length
and is bicoloured with grey to greyish-brown
above and whitish underneath.
The skull has a short incisive foramen tapered in the posterior
region, and the incisors protrude slightly beyond the nasal bones when the
skull is viewed in dorsal profile (Fig. 119). The second upper molar lacks a
posterior loop (Fig. 111), the third upper molar has four inner salient angles
(Fig. 115), and the first lower molar has five or six closed triangles (Fig. 113).
External measurements: TL= 142 (120–165)
n=95, TV= 38 (29–51) n=95, HF= 18 (16–22)
n=92, E= 12 (9–14) n=11, WT= 31.6 (22.0–
45.0) n=14.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: its distribution
overlaps with the Meadow Vole
(M. pennsylvanicus) and Long-tailed Vole
(M. longicaudus) in British Columbia. It
could also be confused with the Heather
Vole (P. intermedius).
See previous account for diagnostic traits of M. longicaudus. M. pennsylvanicus
lacks the grizzled salt and pepper pelage and the dorsal surfaces of its hind feet
are darker. Its second upper molar has a distinct posterior loop (Fig. 110).
P. intermedius has softer, finer fur, more brownish dorsal pelage, a thinner
more sparsely furred tail, and lower molars with the inner re-entrant angles
deeper than the outer re-entrant angles (Fig. 104).
range: the dry interior grasslands including the
Kettle, Similkameen, Okanagan, Thompson, and
Fraser river valleys north to the Chilcotin.

SPECIES ACCOUNTS 127
Microtus oeconomus (Tundra Vole)
description: the dorsal pelage has
tinges of yellow on the flanks and rump;
the undersides are buffy-yellow. The
tail is short, less than 30% of the total
length, and strongly bicoloured. The
skull is characterized by the second
upper molar lacking a posterior loop
(Fig. 111) and the third upper molar
having four inner salient angles (Fig. 115).
The first lower molar usually has only four
closed triangles (Fig. 112)-fewer than any
other British Columbia species of Microtus.
External measurements: TL= 160 (133–179) n=48,
TV= 37 (29–45) n=48, HF= 19 (17–22) n=47, E=
14 (12–16) n=27, WT= 53.0 g (36.1–69.0) n=23.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: its distribution overlaps
with the Meadow Vole (M. pennsylvanicus) and
Long-tailed Vole (M. longicaudus) in northern
British Columbia. See the M. longicaudus
account for diagnostic traits. M. pennsylvanicus
lacks the yellow on flanks and rump, has grey
ventral pelage, and a tail that is not strongly
bicoloured; its second upper molar has a
posterior loop and the first lower molar has
more than four closed triangles.
range: extreme north-western British Columbia from
the Haines Triangle east to the Cassiar Mountains.

128 SPECIES ACCOUNTS
Microtus oregoni (Creeping Vole)
description: our smallest
species of Microtus (weight< 30 g),
it has tiny eyes (less than 3 mm in
diameter) and a short tail (< 30%
of the total length). The fur is short,
almost shrew-like. Although a
number of authorities (Ingles 1965;
Hall 1981) have noted that this
species has only five pads on the
sole of its hind foot (most species
of Microtus have six), this trait needs to be confirmed in a large series of live
animals or fresh specimens. The skull is characterized by the third upper
molar with three inner salient angles (Fig. 114), a pattern found in no other
British Columbian species of Microtus.
External measurements: TL= 135 (122–153)
n=90, TV= 34 (28–42) n=90, HF= 18 (16–20)
n=89, E= 10 (9–13) n=43, WT= 21.5 g (10.0–
31.0) n=59.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: in southwestern British
Columbia this species co-occurs with M.
longicaudus, M. pennsylvanicus, M. richardsoni
and M. townsendii. Diagnostic traits for identifying
M. oregoni include: short fur, small eye
(

SPECIES ACCOUNTS 129
Microtus pennsylvanicus
(Meadow Vole)
description: the dorsal pelage
colour is variable ranging from grey to
brown; the undersides are grey to whitish.
The tail is usually less than 30% of
the total length (20-32%). The skull is
characterized by: the second upper
molar with a posterior loop (Fig. 110),
a trait found in no other British Columbian species of Microtus, the third
upper molar with four inner salient angles (Fig. 115), and the first lower molar
with five or six closed triangles (Fig. 113).
External measurements: TL= 147 (120–186)
n=251, TV= 38 (24–49) n=256, HF= 19 (16–26)
n=259, E= 12 (7–17) n=218, WT= 34.9 (20.0–
63.5) n=262.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: its distribution overlaps
with five other Microtus species in British
Columbia but it can only be confused with the
Montane Vole (M. montanus), Tundra Vole
(M. oeconomus), and Townsend’s Vole (M.
townsendii). See those species accounts for distinguishing
external traits. The presence of a
posterior loop on the second upper molar is
diagnostic.
range: entire mainland east of the coastal mountain
ranges.

130 SPECIES ACCOUNTS
Microtus richardsoni
(Water Vole)
description: our largest Microtus species, with a hind foot greater than
28 mm and an adult weight usually more than 90 grams. The dorsal pelage is
dark grey or grizzled brown; the
undersides are grey. The tail is
long (> 50 mm, and 26-39% of the
total length) and thick. Although
authorities such as Ingles (1965)
and Hall (1981) reported that the
hind foot has only five pads on its
sole, I have observed a small
vestigal sixth pad on some specimens
of this species. The skull is
large (maxillary toothrow length
>7 mm) with the incisive foramina
long and tapered posteriorly (Fig. 117); the nasal bones protrude well beyond
the incisors in dorsal view (Fig. 116). The second upper molar lacks a posterior
loop (Fig. 111), the third upper molar has four inner salient angles (Fig. 115),
and the first lower molar has five or six closed triangles (Fig. 113).
External measurements: TL= 239 (177–276) n=57,
TV= 78 (54–98) n=56, HF= 29 (24–34) n=58,
E= 14 (12–20) n=58, WT=151.2g (124.0–1777.3)
n=12.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: its distribution overlaps
with the Creeping Vole (M. oregoni), Meadow
Vole (M. pennsylvanicus) and Long-tailed Vole
(M. longicaudus) in British Columbia; see those
accounts for diagnostic traits.
range: there are two separate distributional areas in
British Columbia: the Cascade and southern Coast
mountains and the Columbia and Rocky mountains.

SPECIES ACCOUNTS 131
Microtus townsendii
(Townsend’s Vole)
description: a large Microtus with a
hind foot usually greater than 21 mm, and
a tail more than 50 mm. The Triangle
Island population (M. t. cowani) demonstrates
gigantism with some adults more
than 100 g. The dorsal pelage is dark
brown; the undersides are grey to white.
The skull has a narrow incisive foramen
that is not tapered anteriorly or posteriorly;
the incisors protrude slightly beyond the
nasal bones when the skull is viewed
dorsally (Fig. 119). The second upper molar lacks a posterior loop (Fig. 111),
the third upper molar has four inner salient angles (Fig. 115), and the first
lower molar has five or six closed triangles (Fig. 113).
External measurements: TL= 192 (155–184) n=
142, TV= 58 (42–75) n=153 (19–29), E= 14 (10–
18) n=65, WT= 59.6 g (40.0–103.0) n=89.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: the distribution of M.
townsendii overlaps with that of M.
longicaudus and M. oregoni in the lower Fraser
valley. See those accounts for diagnostic traits.
range: Vancouver Island and various associated
smaller islands and the lower Fraser
River valley east to Chilliwack.

132 SPECIES ACCOUNTS
Ondatra zibethicus (Muskrat)
description: the largest vole
in the province, it has large hind
feet that are partially webbed with
stiff hairs on their edges. The tail is
scaly and flattened laterally The
rich pelage has a short dense
underfur with long, glossy guard
hairs. The skull is large (skull length
>40.0 mm, maxillary toothrow length >14.0 mm) with rooted cheek teeth.
External measurements: TL= 547 (448–685) n=140, TV= 242 (195–295) n=138,
HF= 76 (63–85) n=137, E= 23 (19–26) n=26,
WT=1.02 kg (0.70–1.77) n=40.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: none.
range: the entire mainland of the province;
introduced to Vancouver Island and the Queen
Charlotte Islands.

SPECIES ACCOUNTS 133
Phenacomys intermedius (Heather Vole)
description: a small vole with soft fine fur.
The dorsal pelage ranges from brown to
greyish-brown; undersides are grey or
whitish. Some northern populations
have a yellow wash on the nose. The
dorsal surface of the hind feet is whitish.
The tail is short (< 30% of the total
length), thin (even at its base), and
sparsely furred. The cheek teeth are
rooted; the lower molars have inner
re-entrant angles deeper than the outer
re-entrant angles (Fig. 104).
External measurements: TL= 137 (120–164)
n=82, TV= 33 (21–46) n=84, HF= 18 (15–22)
n=83, E= 14 (10–16) n=24, WT= 32.1 g (24.0–
50.0) n=21.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: in external appearance
this vole is difficult to distinguish from
some Microtus species especially immature
animals. P. intermedius has softer, finer fur;
the dorsal surfaces of its hind feet are white
or silvery rather than black; and the tail is thin with a sparse covering of
hairs. The enamel patterns on the lower molars are diagnostic—no Microtus
species has lower molars with deeper inner re-entrant angles.
range: most of the mainland of the province but
absent from coastal islands.

134 SPECIES ACCOUNTS
Synaptomys borealis
(Northern Bog Lemming)
description: a small vole with a
short tail (< 20% of the total length)
that is equal to or slightly longer
than the hind foot length. The fur is
long and coarse. The dorsal pelage
is grizzled brown or greyish-brown
and the undersides are grey. The
ventral side of the tail is sparsely
covered with greyish or whitish hairs. The skull has a short rostrum with
grooved upper incisors. The re-entrant angles on the upper molars are deeper
on the outer side and extend to the inner border of the tooth in the first and
second molars (Fig. 96). The lower molars lack closed triangles on the outer
sides (Fig. 102).
External measurements: TL= 123 (102–142)
n=91, TV= 22 (17–30) n=90, HF= 19 (14–22)
n=89, E= 12 (6–15) n=20, WT= 26.4 g (21.7–
48.0) n=13.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: the short tail and distinctive
enamel patterns on its upper and
lower molars discriminate this species from
any other British Columbia vole.
range: most of the mainland of the province and a
few near shore coastal islands.

SPECIES ACCOUNTS 135
Subfamily Murinae: Old World Rats and Mice
There are three species in British Columbia; all are alien species introduced
from Europe or Asia. They have naked tails with visible annulations (Fig. 44).
Their skulls have rooted molars, and the cusps of the first two upper molars
are arranged in three longitudinal rows (Fig. 98).
Mus musculus (House Mouse)
description: a small ‘mouselike’
rodent with a long, naked scaly
tail and small ears. The dorsal fur is
dull grey-brown, and the ventral
fur is grey. The small and delicate
skull has upper incisors that are
notched in side view (Fig. 124).
External measurements: TL= 163 (142–197)
n=41, TV= 79 (64–90) n=48, HF= 18 (15–23)
n=45, E= 13 (11–18) n=15, WT=21.4 g (17.0–
26.0) n=19.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: could be confused with
the Deer Mouse (Peromyscus maniculatus)
and Western Harvest Mouse (Reithrodontomys
megalotis). P. maniculatus has a
brown dorsal pelage with white ventral fur,
the tail is haired (Fig. 45), and its skull has the
cusps of the first two upper molars arranged
in two longitudinal rows (Fig. 123). R.
megalotis is smaller (adult weight < 15 grams), the tail is furred, the upper
incisors are distinctly grooved (Fig. 127), and the cusps of the first two upper
molars are arranged in two longitudinal rows .
range: found in human dwellings; feral populations
occur on the southern coast including the Gulf Islands
and in the southern interior of British Columbia.

136 SPECIES ACCOUNTS
Rattus norvegicus (Norway Rat)
description: a stout rat with a thick naked tail that is shorter (70–90%)
than the head and body length, small ears that
do not cover the eye when pushed forward,
a blunt snout, and a thick heavy rump
(Fig. 48). Dorsal fur is brown and
the undersides are pale grey. The
skull has a rectangular braincase
with straight temporal ridges (Fig.
125); the upper incisors are not
notched in side view.
External measurements: TL= 385
(334–436) n=14, TV= 175 (143–202) n=14,
HF= 42 (34–44) n=14, E= 20 (18–23) n=5,
WT=354.4 g (256.5–434.5) n=5.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: immature animals
especially can be confused with the Black
Rat (Rattus rattus). Diagnostic traits of R.
rattus are: a slender body with a light rump,
tail longer than head and body length,
pointed snout, a large ear that covers the
eye when pushed forward (Fig. 47), and a
skull with a rounded braincase and curved
temporal ridges (Fig. 126).
range: found in urban areas; feral populations occur
in the Vancouver area, the Queen Charlotte Islands
and Vancouver Island.

SPECIES ACCOUNTS 137
Rattus rattus (Black Rat)
description: a slender rat with a
gracile naked tail that is longer (100-
160%) than the head and body length,
large ears that cover the eye when
pushed forward, a pointed snout, and
light slender rump (Fig. 47). Three
distinct colour morphs are found in
British Columbia: 1) alexandrinus
morph—grey-brown dorsal pelage
with slate-grey belly; 2) rattus
morph—black dorsal pelage with a
slate-grey belly; and 3) frugivorous
morph—grey-brown dorsal pelage
with a white to yellow belly. The three
colour morphs can be found at the
same locality. The skull has a rounded
braincase with curved temporal ridges
(Fig. 126); the upper incisors are not
notched in side view.
External measurements: TL= 393 (330–
455) n=60, TV= 216 (172–255) n=59,
HF= 37 (32–42) n=60, E= 23 (21–25) n=14,
WT=185.6 g (119.0–267.8) n=23.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: immature animals especially
can be confused with R. norvegicus;
see that account for distinguishing traits.
range: found in
urban dwellings; feral
populations occur on
the southwestern
coastal mainland and
various coastal islands including the Queen Charlotte
Islands and Vancouver Island.

138 SPECIES ACCOUNTS
Subfamily Sigmondontinae: New World Rats and Mice
The group demonstrates a diversity of body forms but all British Columbian
species have long furred tails, a gracile body (Fig. 42), and conspicuous ears
and eyes. The molars are rooted with two rows of cusps (except for the Bushytailed
Woodrat, Neotoma cinerea).
Neotoma cinerea
(Bushy-tailed Woodrat)
description: superficially this
species resembles a squirrel, with a
long bushy tail and conspicuous
vibrissae. The dorsal pelage is grey
to brown; the ventral pelage and
dorsal surface of the feet are white.
Males have a ventral gland that deposits
a brown stain on the belly fur. The soles of the feet are furred. The skull
is large (skull length >40.0 mm); the crowns of molars superficially resemble
those of a vole with triangles or prisms of
enamel (Fig. 97).
External measurements: TL= 383 (318–468)
n=223, TV= 166 (128–205) n=217, HF= 45 (37–
57) n=222, E= 30 (23–40) n=43, WT= 374.7 g
(315.0–425.0) n=7 males; 326.9 g (292.0–394.6)
n=13 females.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3
similar species: in external appearance
this species could be confused with a squirrel,
but the pelage colour, long vibrissae that extend
to the shoulders, and five digits on the
front feet distinguish N. cinerea from any of
our squirrel species.
The V-shaped infraorbital foramen and prismatic molars
readily distinguish the skull of N. cinerea from any
squirrel (Sciuridae) skull.
range: the entire mainland of British
Columbia but absent from coastal islands.

SPECIES ACCOUNTS 139
Peromyscus keeni (Keen’s Mouse)
description: a ‘mouse-like’ rodent
with a long furred tail and
conspicuous vibrissae. This species
demonstrates considerable size and
fur colour variation, particularly
among island populations. Typically,
the dorsal pelage is brown to
dark grey. Some island populations,
however, are very dark and have a
dorsal band that is nearly black.
The undersides are generally white
to grey, but one insular subspecies
associated with the Hunter Island
group on the central coast of British Columbia (i.e., P. k. rubriventer) has
distinctive reddish-brown markings on its chest and belly. The dorsal surface
of the hind feet vary from white or silver to dark brown. The skull is
characterized by molars with cusps and incisors
that lack grooves.
External measurements: TL= 198 (140–263) n=773,
TV= 102 (70–126) n=772, HF= 24 (19–32) n=773,
E= 18 (12–26) n=327, WT= 26.0 (15.0–52.4)
n=774.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3.
similar species: the only similar species is
the Deer Mouse (Peromyscus maniculatus). Their
distributions overlap on the southern coastal
mainland, the eastern slopes of the Cascade and
Coast mountains, Vancouver Island, and a few
associated islands. The two species differ in
chromosomes and other genetic traits but identification from external morphology
in these regions is problematic. Adult P. maniculatus generally have
a shorter tail (< 98 mm) (Gunn and Greenbaum 1986; Allard and Greenbaum
1988) but this measurement overlaps to some extent among some populations
of P. keeni and P. maniculatus. Similarly, although P. keeni averages larger than
P. maniculatus in most cranial measurements, the two species can not be
discriminated by any single skull measurement. Based on specimens identified
from western Washington, and islands and coastal areas of southwestern

140 SPECIES ACCOUNTS
British Columbia that were identified from genetic traits, Allard and
Greenbaum (1988) developed a discriminant function using tail length and
length of the mandibular diastema that reliably discriminated the two species.
However, this can not be used on live animals as it requires a skull, and its
reliability needs to be assessed in other regions (e.g., the east slopes of the
coastal mountain ranges) where the two species co-occur. Immature
Peromyscus can only be identified to species from genetic traits.
range: the coastal mainland east to the eastern
slopes of the coastal mountain ranges, the north coast
islands including the Queen Charlotte Islands, Vancouver
Island and some associated islands off the
north and west coast of Vancouver Island.

SPECIES ACCOUNTS 141
Peromyscus maniculatus (Deer Mouse)
description: a ‘mouse-like’ rodent
with a long furred tail, and conspicuous
vibrissae. The dorsal fur is brown
with a white belly and white on the
dorsal surface of the hind feet. Some
island populations of the coastal subspecies
P. m. austerus tend to be very
dark, whereas populations of the P. m.
artemisiae in the dry interior are pale.
Nevertheless, this species is less variable in fur colour than Keen’s Mouse
(Peromyscus keeni). The skull has molars with cusps and the incisors lack
grooves.
External measurements: TL= 170 (125–209) n=1519,
TV= 80 (50–104) n=1521, HF= 21 (15–28) n=1521,
E= 17 (10–22) n=662, WT= 21.7 (15.0–41.8)
n=1521.
Dental Formula: incisors 1/1, canines 0/0, premolars
0/0, molars 3/3
similar species: on the southern coast and
east slopes of the coastal mountain ranges distinguishing
this species from P. keeni is problematic
(see previous species account). In the Okanagan
region, P. maniculatus could be confused with the
Western Harvest Mouse (Reithrodontomys
megalotis). R. megalotis is smaller; adults have a total length less than 150 mm
and weigh less than 15 g. Any P. maniculatus that are similar in size to R.
megalotis are obvious juvenile animals that can be discriminated by their dull
grey pelage. The skull of R. megalotis has distinct grooves on the anterior face
of the upper incisors and is smaller (skull length

142 SPECIES ACCOUNTS
Reithrodontomys megalotis (Western Harvest Mouse)
description: the smallest
‘mouse’ in British Columbia, it
has a reddish-brown dorsal fur
and white underparts. The tail
is slender and sparsely haired.
The small delicate skull has
molars with two rows of
cusps (Fig. 123), and upper
incisors with grooves on their
anterior face (Fig. 127).
External measurements: TL=
136 (116–151) n=42, TV= 67 (54–86) n=42,
HF= 16 (12–19) n=42, E= 14 (12–17) n=14,
WT= 11.0 g (8.0–15.0) n=38.
Dental Formula: incisors 1/1, canines 0/0,
premolars 0/0, molars 3/3
similar species: could be confused
with the House Mouse (M. musculus) and
Deer Mouse (P. maniculatus). See those
accounts for diagnostic traits.
range: confined
to the Okanagan
Valley and southern
Similkameen
Valley.

SPECIES ACCOUNTS 143
FAMILY DIPODIDAE: JUMPING MICE AND JERBOAS
Small mouse-like rodents that have elongated hind limbs and hind feet, and
long, nearly naked tails (Fig. 46). The skull has a large oval infraorbital
opening (Fig. 89) and rooted cheek teeth that are high crowned with distinct
transverse ridges.
Zapus hudsonius
(Meadow Jumping Mouse)
description: our smallest jumping
mouse, it has bright yellow to buff sides,
a grey dorsal band, and whitish undersides
typically with buffy patches on the
belly, chest, and throat. The skull is small;
the upper premolar is simple lacking a
crescent fold at the base of the main cusp
(Fig. 94).
External measurements: TL= 213 (190–
237) n=113, TV= 130 (114–149) n=111, HF= 31
(28–34) n=110, E= 13 (10–16) n=32, WT= 16.7 g
(10.0–25.0) n=34.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/0, molars 3/3.
similar species: throughout most of its
range in the province, this species co-occurs
with the Western Jumping Mouse (Zapus princeps).
In most areas where the two species cooccur,
Z. princeps is slightly larger and has
duller sides that range from yellow to grey and
white undersides that lack a buffy wash or
buffy patches. Nonetheless, because both species show considerable variation
in pelage colour, distinguishing the two taxa from external traits is exceedingly
difficult in some regions. Positive identification
can only be made from the skull, with the skull of
Z. princeps being larger (incisive foramen length
> 4.2 mm and a maxillary toothrow length> 3.7 mm).
range: across northern and southern British
Columbia as far south as the Okanagan Valley
in the central interior.

144 SPECIES ACCOUNTS
Zapus princeps (Western Jumping Mouse)
description: the dorsal pelage has a grey
dorsal band and dull yellow to grey sides.
The undersides usually lack a buffy wash
or buffy patches on the throat (except
some populations of the subspecies
kootenayensis), chest, or abdomen. The
upper premolar is simple lacking a
crescent fold at the base of the main
cusp (Fig. 94).
External measurements: TL= 235 (209–
265) n=218, TV= 142 (122–162) n=218,
HF= 32 (27–34) n=220, E= 12 (10–16)
n=81, WT= 24.6 g (17.7–37.5) n=68.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/0, molars 3/3
similar species: to distinguish from
Meadow Jumping Mouse Z. hudsonius
see that species account. In southwestern
British Columbia, this species coexists
with the Pacific Jumping Mouse
(Zapus trinotatus) in a narrow zone along
the crest of the Cascade Range and the
southern Coast Mountains. Although
Z. trinotatus tends to be more brightly
coloured with buffy wash and buffy
patches on the ventral pelage, and its
upper premolar has a crescent fold at
the base of the main cusp (Fig. 93), these traits tend to be variable. Distinguishing
the two species in this contact zone is problematic.
range: the entire mainland except for extreme southwestern
British Columbia, where it is replaced by the
Pacific Jumping Mouse (Z. trinotatus).

SPECIES ACCOUNTS 145
Zapus trinotatus (Pacific Jumping Mouse)
description: a large
brightly coloured jumping
mouse. The dorsal pelage
has bright yellow to light
orange sides that contrast
sharply with the dark dorsal
band. The undersides
are usually white, washed
with buff; buffy patches
may occur on the throat,
chest, and abdomen. The
upper premolar is complex
with a crescent fold at
the base of the main cusp
(Fig. 93).
External measurements: TL= 237 (215–258)
n=87, TV= 144 (123–162) n=86, HF= 32
(29–31) n=86, E= 14 (12–16) n=10, WT=
24.2 (17.0–36.0) n=20.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/0, molars 3/3
similar species: see previous accounts
for distinguishing from Z. princeps.
range: extreme
southwestern
British Columbia
where it ranges
as far north as
Garibaldi Provincial Park and east to the Allison
Pass area in Manning Provincial Park.

146 SPECIES ACCOUNTS
FAMILY ERETHIZONTIDAE: NEW WORLD PORCUPINES
Erethizon dorsatum (Porcupine)
description: a large rodent with
long stiff spines, particularly on
the tail and rump. The skull is
massive with a round infraorbital
opening that exceeds the foramen
magnum in size.
External measurements: TL= 795 (657–
932) n=34, TV= 231 (170–330) n=86,
HF= 107 (84–124) n=86, E= 24 (15–34)
n= 6, WT= 9.1 kg (4.3–12.3) n=18 males;
5.6 kg (3.3–8.4) n=9 females.
Dental Formula: incisors 1/1, canines 0/0,
premolars 1/1, molars 3/3
similar species: none.
range: most of the
mainland; absent from
the coastal islands.

Glossary of Technical Terms
147
Annulations: scaly rings on the tail.
Auditory Bulla: bony capsule that covers the middle and inner ear.
Alveolus: socket in the upper or lower jaw in which the root of a tooth is set.
Angular Process: bony projection on the mandible or jaw bone that lies
below the point where the jaw articulates with the skull (Figs. 2, 3)
Baculum: male genital bone (os penis bone); an important identification
trait in chipmunks (Fig. 145).
Basilar Length: a measurement of skull length taken from the mid-ventral
border of the foramen magnum to the anterior border of the
alveoli of the median incisor (Fig. 81).
Basioccipital: ventral portion of the bone surrounding the foramen
magnum.
Baubellum: female genital bone (os clitoris bone); an important identification
trait in chipmunks (Figs. 146, 147, 148).
Body Length: total length minus tail vertebrae length, i.e., length excluding
the tail (Fig. 7).
Calcar: a cartilaginous spur in some bats that projects from the ankle along
the edge of the tail membrane. The presence or absence of a calcar
is an important identification trait.
Canine: tooth posterior to the incisors and anterior to the premolars (Fig.
70); a single canine occurs on each side of the upper and lower
jaws in mammals. Canines are usually long and dagger-like but are
flattened in the moles.
Cheek Teeth: general term referring to the premolars and molars.
Cingulum: an enamel shelf that lies below the cusp or peak of a tooth; in
shrews the cingulum on the upper unicuspid teeth is on the inside
or tongue side of the unicuspid (Figs. 65, 67).
Cusp: a high peak or rounded area on the crown of a tooth.

148 GLOSSARY OF TECHNICAL TERMS
Dentine: hard ivory-like substance beneath the enamel of teeth. In some
rodents such as voles the dentine is exposed on the crown surface
of the molar teeth (Fig. 96, 97).
Dorsal: the back or upper surface.
Ear Length: length of the ear measured from the ear notch (Fig. 7).
Enamel: the hard outer layer of the crown of the tooth (Fig. 96, 97).
Usually white but may be yellow or brown in some rodents and red
in some teeth of shrews.
Fenestrate: with openings or perforations (Fig. 4).
Foramen Magnum: large opening at the rear of the skull through which
the spinal cord passes.
Forearm Length: length of the bat forearm measured from wrist to elbow
(Fig. 7).
Hind Foot Length: length of the hind foot measured from the edge of the
heel to the end of the longest claw (Fig. 7).
Incisors: anterior-most teeth in the mammalian skull and jaw; teeth
preceding the canines (Figs. 51, 70, 87).
Incisive Foramen: a pair of openings that pierce the palate behind the
incisor teeth (Fig. 87).
Incisive Foramen Length: a measure of the length of the incisive foramen
(Fig. 95).
Infraorbital Opening: an opening that passes through the side of the
rostrum to the front face of the orbit of the skull (Figs. 89-92).
Interorbital Region: the dorsal area of the skull that lies between the orbits.
Interparietal Bone: an unpaired bone at the back of the braincase (Fig. 84).
Mandible: lower jaw.
Marsupium: abdominal pouch of marsupials where young are carried and
nursed.
Maxilla: bone in the upper jaw that supports the canine, premolar, and
molar teeth.
Maxillary Toothrow Length: length of the upper toothrow (usually
excluding incisors) taken at the alveoli (Figs. 71, 81, 87).
Medial: lying in or near the plane that divides the skull into two mirror
image halves.

GLOSSARY OF TECHNICAL TERMS 149
Melanism: fur colour mutation where fur colour is black.
Molars: last teeth in the jaws, posterior to premolars (Figs. 51, 70, 87).
Number varies among mammals but the maximum number is
four on each side of the upper and lower jaws (e.g., opossums).
Opposable: positioned opposite; in the North American Opossum the
large toe is positioned opposite to the other toes (Fig. 1).
Palatal Length: length of the palate measured from the posterior border of
the palate to the anterior border of the alveolus of the median
incisor (Fig. 52).
Pelage: fur; the hairs of a mammal.
Prehensile: adapted for grasping as in the tail of the North American Opossum.
Premolars: teeth following the canine and preceding the molars (Figs. 51,
70). Number of premolars varies among mammals but the maximum
number (e.g., moles) is four on each side of the upper and
lower jaws.
Ramus: vertical posterior part of the jaw bone.
Re-entrant angle: inward pointing angle along the margin of vole molars
(Fig. 88).
Rostrum: the nasal area or snout of a skull.
Salient angle: outward pointing angle along the margin of vole molars
(Fig. 88).
Skull Length: length of the skull measured from posterior border of occipital
foramen to the anterior border of rostrum (Figs. 52, 71, 87)
Supraorbital Processes: bony projection above the orbit of the skull; well
developed in lagomorphs (Fig. 84).
Tail Vertebrae Length: length of the tail measured from the base to last
vertebra (Fig. 7).
Temporal Ridges: a prominent ridge traversing the side or top of the
braincase (Fig. 125).
Tine: in shrews refers to the small, pointed accessory cusps found on the
middle of the anterior face of the upper incisor (Fig. 16, 17). The
presence or absence of medial tines and their size and position
relative to the pigmented area on the face of the incisor is an
important identification trait.

150 GLOSSARY OF TECHNICAL TERMS
Total Length: length measured from tip of the nose to last tail vertebra (Fig. 7).
Tragus: a thin cartilaginous structure attached to the base of the ear in bats.
Tragus Length: length of tragus measured from its tip to where it is
attached at the notch of the ear.
Unicuspid: in shrews refers to a series of five teeth in the upper jaw and
one or two teeth in the lower jaw that follow the incisor and are
characterized by having a single cusp (Fig. 51). The relative size of
the upper unicuspids is an important identification trait.
Ventral: the under or lower surface.
Vertebra (pl. vertebrae): one of the small bones making up the backbone
Vibrissae: long tactile hairs on the face; whiskers.
Zygomatic Arch: an arch of bone that extends across the orbit of the eye in
the skull (Fig. 53). Not found in the shrew skull but present in
opossum, mole, bat, lagomorph, and rodent skulls.
Zygomatic Plate: a thin plate extending from the zygomatic arch to the
rostrum (Figs. 99, 100).
Zygomatic Process of Maxilla: projection of the maxilla bone that forms
the anterior part of the zygomatic arch.

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